The Relationships Between Wildlife Openings and Avian Use and Abundance in the East Gulf Coastal Plain by Carrie Bert Johnson A thesis submitted to the Graduate Faculty of Auburn University in partial fulfillment of the requirements for the Degree of Master of Science Auburn, Alabama December 13, 2010 Keywords: abundance, bird use, occupancy, wildlife opening, Alabama, coastal plain Copyright 2010 by Carrie Bert Johnson Approved by James B. Grand, Chair, Professor of Wildlife Sciences Gary R. Hepp, Professor of Wildlife Sciences Eric C. Soehren, Terrestrial Zoologist, AlabamaDCNR, State Lands Division ii Abstract Wildlife openings are forest openings created predominately for game species. Many bird species, some of which are exhibiting population declines, utilize openings during the breeding season. Openings can vary in size, shape, edge length, forest type, and management style. Point counts were conducted in openings of 2 study areas in south Alabama. We used occupancy analysis to determine how bird use as well as bird abundance were related to those 5 characteristics of openings. We incorporated detection into our analysis to account for imperfect detections. Bird use for many bird species showed strong relationships to size, edge, and management, while abundance for many species was strongly related to size, shape and management. Forest type did not have strong relationships with either use or abundance. These results may be incorporated into management plans to increase or control species distributions as well as to help maintain abundances of species of interest. iii Acknowledgments Project funding was provided by the Alabama Department of Conservation and Natural Resources State Wildlife Grants and The School of Forestry and Wildlife Sciences at Auburn University. I would like to give great thanks to my committee including Dr. Barry Grand, Dr. Gary Hepp, and Eric Soehren for their guidance and support throughout my graduate career. I would also like to thank my collegues in the Alabama Cooperative Fish and Wildlife Research Unit, especially Amy Silvano, Alan Hitch, and Mark Mackenzie for their support and help throughout this process. For administrative support I would like to thank Judy Christian. I would like to thank my research technicians for their help collecting field work: Paige Aplin, Marcus Collado, Mike Gagin, Donna Hestermann, Karen Tenaglia, and Erika Taketa. Last I would like to thank family and friends, especially Todd Threadgill for their support. iv Table of Contents Abstract ?????????????????????????????..?....ii Acknowledgments ????????????????????...????...?..iii List of Tables ...?????????????????????????.?...?.vi List of Figures ???????????????????????????..?.ix Chapter I: Introduction ????????.....???? ???????????......1 Literature Cited ????????????????????????......7 Chapter II: The Relationship Between Probability of Avian Use and Wildlife Openings in the East Gulf Coastal Plain ????????.....???????????.11 Abstract ????????????????????????????11 Introduction ??????????????????????????..12 Study Areas and Methods ????????...??????????.?....14 Hypotheses ...???????????????????????..17 Analysis ?????????????????????????..19 Results ??????????????????????????..??20 Discussion ???????????????????????????24 Literature Cited ????????????????????????....34 Tables and Figures ???..????????????????????.40 Chapter III: The Relationship Between Avian Density and Wildlife Openings in the East Gulf Coastal Plain ????????????? ??????????....62 v Abstract ????????????????????????????62 Introduction ??????????????????????????..63 Study Areas and Methods ????????????????????....66 Hypotheses ...????????...?????????????.?..68 Analysis ??????????...??????? ????.???..69 Results ????????????????????????????..70 Discussion ??????????????????????????....74 Literature Cited ?????????????????????????83 Table and Figures ????????????????????????.88 Chapter IV: Conclusions ???????????????????????....111 Appendix ???? ??.???????????????????????...114 vi List of Tables Table 2.1: Hypotheses and corresponding models for species detection rates for birds on Barbour WMA and Stimpson and Upper State Sanctuaries, Alabama 2008- 09.????????????????????.???? ????... 40 Table 2.2: Hypotheses and corresponding models for occupancy rates of birds encountered on Barbour WMA and Stimpson and Upper State Sanctuaries, Alabama 2008-09..???????..????????....... ?????.41 Table 2.3: Best detection models (?<2.0) for each species of bird1 observed in wildlife openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain of Alabama, 2008-09. For this comparison, detection models were fit with a null model of occupancy ( .). Species with more than one best model appear under multiple models?? ????? ????....42 Table 2.4: The relative importance of the area model (?area) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09......??????????????..???? ?????..?.44 Table 2.5: The relative importance of the edge model (?edge) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09???????????????????...?? ?. ???...46 Table 2.6: The relative importance of the shape model (?shape) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09...????????????????..?...? ..??????.48 vii Table 2.7: The relative importance of the surrounding forest type model (?forest) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09...??????????????? ?? ??...49 Table 2.8: The relative importance of the opening management model (?management) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09...???????????????? .?. ??.50 Table 2.9: The relative importance of the null model (?.) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09...?????????????????????. ? ???...52 Table 3.1: Hypotheses and corresponding models for detection rates of birds detected on Barbour WMA and Stimpson and Upper State Sanctuaries, Alabama 2008- 09????? ??????????????????? ...??...?...88 Table 3.2: Hypotheses and corresponding models for abundance for birds encountered on Barbour WMA and Stimpson and Upper State Sanctuaries, Alabama 2008- 09????? ?.????????????????...?? .???....89 Table 3.3: Best fit detection models (?<2.0) for each species of bird1 observed on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain of Alabama, 2008-09. For this comparison, detection models were fit with a null model of abundance (?.). Species with more than one best model appear under multiple models.??.??????????? ????...90 Table 3.4: The relative importance of the area model (?area) of density as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09...???????????????? ?.. ..?.......?.92 Table 3.5: The relative importance of the edge model (?edge) of density as indicated by model likelihood and weights for species found in openings on Barbour viii Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09????????????????? ?.... ???...94 Table 3.6: The relative importance of the shape model (?shape) of density as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09????????????????.. ? ?????.95 Table 3.7: The relative importance of the surrounding forest type model (?forest) of density as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09?????????. .? ????...97 Table 3.8: The relative importance of the opening management model (?management) of density as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09...???????????? .??.98 Table 3.9: The relative importance of the null model (?.) of density as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09..????????????????????.. ?? ???.100 ix List of Figures Figure 2.1: Grid for vegetation analysis?..??????...??????.?? ??..54 Figure 2.2: The relative sensitivity of bird species use of the size of wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain? ???? ..?????...????????? ..?....??.55 Figure 2.3: The relative sensitivity of bird species use to the amount of edge surrounding wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain..?????????. ..?? ?.?.??? ..56 Figure 2.4: The relative sensitivity of bird species use to the shape of wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain.??. ..???.??????????????. .?...?.?.57 Figure 2.5a: The relative sensitivity of bird species use to the deciduous forest type surrounding wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain...????????.??? ?..58 Figure 2.5b: The relative sensitivity of bird species use to the mixed forest type surrounding wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain?.????????.?? ??59 Figure 2.5c: The relative sensitivity of bird species use to the pine forest type surrounding wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain......??..??????????.? ???60 Figure 2.6: The relative sensitivity of bird species use to the management of wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain..??????...????????..? ????61 x Figure 3.1: Grid for vegetation analysis?...????...?????? ?? ..?..??103 Figure 3.2: Relative sensitivity of bird species density to the size of openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain??.? ???????????????.????? .........??104 Figure 3.3: Relative sensitivity of bird species density to the edge length (perimeter) of openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain????.??????????? ..?..???105 Figure 3.4: Relative sensitivity of bird species density to the shape of openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain..? ???.??????????...?????.???...106 Figure 3.5a: Relative sensitivity of bird species density to deciduous forest surrounding openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain..?...??????..???? ????..???107 Figure 3.5b: Relative sensitivity of bird species density to mixed forest surrounding openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain..?...??????..????? ???..???108 Figure 3.5c: Relative sensitivity of bird species density to pine forest surrounding openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain.................................................................................109 Figure 3.6: Relative sensitivity of the bird species density to management on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain??? ????????????????? .?????.?.....110 1 CHAPTER I: INTRODUCTION Many Neotropical migratory bird species are exhibiting population declines throughout their breeding ranges (Sauer et al. 2007). These declines are caused by many factors including predation and habitat loss. One source of decline that is common throughout the southeastern U.S. is the increase in fragmentation across landscapes. Forest fragmentation is the division of large contiguous tracts of forest habitat into smaller patches (Keyser et al. 1998) by creating early succesional fields, agriculture, and urban development. Fragmentation is a problem on both wintering and breeding grounds but has been found to be more detrimental on breeding grounds of Neotropical migrant species (Hagen and Johnston 1992, B?hning-Gaese et al. 1993). Anthropogenic disturbances are an increasing source of fragmentation throughout the south. One anthropogenic factor that is prevalent throughout the south is the conversion of forest habitat to agricultural fields. This conversion creates early successional areas and decreases the amount of core area available in the forest interior; core area is essential for many species (Robbins et al. 1989). Along with agriculture, increases in logging of hardwood forests (USDA Forest Service 1988) in the southeastern U.S. over the last few decades may be altering the bird communities (Krements and Christie 2000, Lichstein et al. 2002, Wallendorf et al. 2007, Vitz and Rodewald 2007) by creating more early-succesional and edge habitat further fragmenting mature forest stands. Another man-made disturbance that causes fragmentation in forest stands and is 2 prevalent throughout the southeast is the creation of wildlife openings. Wildlife openings are often created for large game animals such as white-tailed deer (Odocoileus virginianus) and wild turkey (Meleagris gallopavo) for supplemental feeding purposes. Frequently, they are planted with row crops such as soybeans (Glycine max) and corn (Zea mays) or forbs such as partridge pea (Chamaecrista fasciculate, Harper 2007). Occasionally openings in forested habitats are maintained as open fields but not managed heavily to provide more hunting opportunities. These openings are created to increase densities of game species while giving hunters an increased chance of harvesting an animal. While little information is known about the importance of wildlife openings to non-target species such as songbirds (Chandler et al. 2009, King et al. 2009), openings have been found to benefit those species at certain times of the year. When openings are planted during spring and summer months for deer and turkey, they also provide good foraging habitat for migrant birds during the breeding season when finding adequate food sources is imperative for adults as well as fledglings (Martin 1988, Anders et al. 1998). Planted forbs such as partridge pea are good for many species such as northern bobwhite (Colinus virginianus) and passerine birds (Harper 2007). Insectivorous species such as blue-gray gnatcatcher (Polioptila caerulea) may also benefit from increased foraging opportunities in wildlife openings. Berries, such as blackberries (Rubus spp.) and blueberries (Vaccinium spp.), often grow along edges and within openings that are not managed intensely or mowed frequently. Along with foraging opportunities, openings also provide suitable nesting habitat and escape cover for some birds. Ground nesters will nest in these openings on bare 3 ground and in warm season grasses like broomsedge (Andropogon spp., Harper 2007). When thickets are present in openings they are often used by non-raptorial birds for nesting and escape cover from avian predators such as red-shouldered hawks (Buteo lineatus). Edge habitat found around openings is often utilized for nesting as well. There are many characteristics of wildlife openings which could affect bird species such as size, shape, edge, surrounding forest type, and management. The size of openings may be important when managing for bird species. Wildlife openings range in size from a small forest clearing of a few trees to large open fields over 50 hectares in size. Openings can differ in size based on the original intent for the opening. When managing for mourning dove or northern bobwhite, openings can to be larger (>5ha). For other game species such as white-tailed deer and eastern cottontail (Silvilagus floridanus), openings can be much smaller forest openings or food plots (e.g., <5ha). With this range in sizes for openings, it is important to know how the opening size affects bird use and abundance. Forest species may be deterred from forests adjacent to larger openings, and early successional species may require a minimum size of opening. One study in Illinois found that bird abundance began to increase in openings of 0.3ha (Overcash and Roseberry 1987). Another characteristic of openings that may have an impact on bird occupancy is the length of edge habitat surrounding the opening (i.e., perimeter length). Nest predators often concentrate along forest edges, possibly because of increased density of nests in and around edge habitat (Wilcove 1985, Paton 1994, King et al. 1998). Also, several studies have suggested that brown-headed cowbirds (Molothrus ater) concentrate along edges which may increase the chance of parasitism on nests (Helzer and Jelinski 1999, 4 Moorman et al. 2002, Howell et al. 2007). If this is the case then brown-headed cowbird occupancy should also show a positive relationship with the amount of edge present in an opening. Therefore, with the increase in edge habitat, predation and parasitism on nests may also increase. While there are negative associations with edge habitat, these areas often provides foraging opportunities as well as escape cover from many avian predators. Some bird species prefer edge habitat along forest edges for breeding as well, so with an increase in amount of edge habitat available within an opening, occupancy as well as density of those species may increase. Multiple species, such as northern cardinal (Cardinalis cardinalis) and field sparrows (Spizella pusilla), nest in thickets and briars along edges of wildlife openings (Fink et al. 2006, Harper 2007, Vitz and Rodewald 2007). When there is more edge habitat available for escape cover and foraging, more forest species may be found along wildlife openings. Therefore, the length of edge of an opening may be an important factor in managing for bird species along with increasing densities within different communities. Similar to area and edge, the shape of the wildlife openings may also be a factor in the probability of bird occupancy for several bird species. Openings can range from irregular and oblong shapes to perfectly round. As an opening becomes more round the edge-to-core ratio of the opening decreases. This ratio is the perimeter of an opening divided by its area; consequently circular openings have the lowest edge-to-core ratio. Forest bird species may prefer openings with large edge-to-core ratios because there is more edge habitat for them to utilize and less open field. Many forest species will avoid flying through open habitats and fields (Desrochers and Hannon 1997). Therefore, the shape of the opening may be an important characteristic for forest species, as well as 5 others. The management of openings can vary greatly depending on intent. Some openings are intensely managed with plowing and planting of supplemental food for wildlife, while others are maintained as pastures or fields with no other management actions. While planted forbs such as common ragweed (Ambrosia artemisiifolia) and partridge pea are good for game species such as northern bobwhite, they also can be good foraging habitat for non-game bird species (Harper 2007). Due to the abundance of food, forest interior species, such as wood thrush (Hylocichla mustelina), may use these openings during the post-breeding season for foraging with their fledglings (Anders et al. 1998, Rivera et al. 1998, Marshall et al. 2003). While certain species, such as white-tailed deer and mourning dove (Zenaida macroura), are the focus of these management actions to create openings, some other species, both game and non-game, are likely affected by management practices. Therefore, it is important to examine the potential affects of management on other species found in the area. Many bird species are associated with certain forest types, so the forest type surrounding an opening may also be a factor affecting their use by some species. One such species is the brown-headed nuthatch (Sitta pusilla), which is primarily associated with mature pine forests (Conner and Dickson 1997, Hamel 1992, Johnston and Odum 1956). Therefore, the likelihood that that species would be found within and around an opening surrounded by pine forest should be much greater than one surrounded by hardwoods. Wildlife openings are often used by migrant bird species yet we have little understanding of the relationships between use and characteristics of openings. To better 6 manage openings for bird species that are declining, it is important to know how species use and density are related to characteristics of openings (size, shape, edge length, management style, and forest type). To determine these relationships, we conducted field surveys on 2 study sites within the East Gulf Coastal Plain of South Alabama. We tested our a priori hypotheses using occupancy models to see if relationships existed between bird occupancies and abundances and characteristics of wildlife openings. 7 LITERATURE CITED Anders, A.D., J. Faaborg, and F.R. Thompson III. 1998. Postfledging dispersal, habitat use, and home-range size of juvenile wood thrushes. Auk 115: 349-358. B?hning-Gaese, K., M.L. Taper, and J.H. Brown. 1993. Are declines in North American insectivorous songbirds due to causes on the breeding range? Conservation Biology 7:76-86. Chandler, R.B., D.I. King, and C.C. Chandler. 2009. Effects of management regime on the abundance and nest survival of shrubland birds in wildlife openings in northern New England, USA. Forest Ecology and Management 258: 1669-1676. Conner, R.N., and J.G. Dickson. 1997. Relationships between bird communities and forest age, structure, species composition, and fragmentation in the west Gulf Coastal plain. Texas Journal of Science 49: 123-138. Desrochers, A. and S.J. Hannon. 1997. Gap crossing decisions by forest songbirds during the post-fledging period. Conservation Biology 11: 1204-1210. Fink, A.D., F.R. Thompson III, A.A. Tudor. 2006. Songbird use of regenerated forest, glade, and edge habitat types. Journal of Wildlife Management 70: 180-188. Hagan, J.M. and D.W. Johnston, editors. 1992. Ecology and conservation of Neotropical migrant landbirds. Smithsonian Institution Press, Washington, D.C. Hamel, P.B. 1992. Land manager?s guide to birds of the south. The Nature Conservancy, Southeastern Region, Chapel Hill, NC. Harper, C.A. 2007. Strategies for managing early succession habitat for wildlife. Weed Technology 21: 932-937. Helzer, C.J., and D.E. Jelinski. 1999. The relative importance of patch area and 8 perimeter-area ratio to grassland breeding birds. Ecological Applications 9: 1448- 1458. Howell, C.A., W.D. Dijak, F.R. Thompson, III. 2007. Landscape context and selection for forest edge by breeding Brown-headed Cowbirds. Landscape Ecology 22: 273-284. Johnston, D.W. and E.P. Odum. 1956. Breeding bird populations in relation to plant succession on the piedmont of Georgia. Ecology 37: 50-62. Keyser, A.J., G.E. Hill, and E.C. Soehren. 1998. Effects of forest fragment size, nest density, and proximity to edge on the risk of predation to ground-nesting passerine birds. Conservation Biology 12:986-994. King, D.I., C.R. Griffin, and R.M. DeGraaf. 1998. Nest predator distribution among clearcut forest, forest edge, and forest interior in an extensively forested landscape. Forest Ecology and Management 104: 151-156. King, D.I., R.B. Chandler, S. Schlossberg, and C.C. Chandler. 2009. Habitat use and nest success of scrub-shrub birds in wildlife and silvicultural openings in western Massachusetts, USA. Forest Ecology and Management 257: 421-426. Krementz, D. G. and J.S. Christie. 2000. Clearcut stand size and scrub-successional bird assemblages. Auk 117: 913-924. Lichstein, J.W., T.R. Simons, and K.E. Franzreb. 2002. Landscape effects on breeding songbird abundance in managed forests. Ecological Applications 12:836-857. Marshall, M.R., J.A. DeCecco, A.B. Williams, G.A. Gale, and R.J. Cooper. 2003. Use of regenerating clearcuts by late successional bird species and their young during the post-fledging period. Forest Ecology and Management 183: 127-135. 9 Martin, T.E. 1988. Habitat and area effects on forest bird assemblages: is nest predation an influence? Ecology 69:74-84. Moorman, C.E., D.C. Guynn Jr., and J.C. Kilgo. 2002. Hooded Warbler nesting success adjacent to group-selection and clearcut edges in a southeastern bottomland forest. Condor 104: 366-377. Overcash, J.L. and J.L. Roseberry. 1987. Evaluation of Shawnee National Forest wildlife openings. Cooperative Wildlife Research Laboratory, SIU-C. Southern Illinois University, Carbondale. Paton, P.W.C. 1994. The effect of edge on avian nest success: how strong is the evidence? Conservation Biology 8: 17-26. Rivera, J.H.V., J.H. Rappole, W.J. McShea, and C.A. Haas. 1998. Wood thrush postfledging movements and habitat use in northern Virginia. Condor 100: 69-78. Robbins, C.S., D.K. Dawson, and B.A. Dowell. 1989. Habitat area requirements of breeding forest birds of the middle Atlantic states. Wildlife Monographs 103. Sauer, J.R., J.E. Hines, and J. Fallon. 2007. The North American Breeding Bird Survey, results and analysis 1966-2006. Version 10.13.2007. USGS Patuxent Wildlife Research Center, Laurel, MD. USDA Forest Service. 1988. The south?s fourth forest; alternatives for the future. USDA Forest Service Forest Resources Report Number 24. Washington DC, USA. Vitz, A.C. and A.D. Rodewald. 2007. Vegetative and fruit resources as determinants of habitat use by mature-forest birds during the postbreeding season. Auk 124: 494- 507. Wallendorf, M.J., P.A. Porneluzi, W.K. Gram, R.L. Clawson, and J. Faaborg. 2007. Bird 10 response to clear cutting in Missouri Ozark forests. Journal of Wildlife Management 71: 1899-1905. Wilcove, D.S. 1985. Nest predation in forest tracts and the decline of migratory songbirds. Ecology 66: 1211-1214. . 11 CHAPTER II: THE RELATIONSHIP BETWEEN PROBABILTY OF AVIAN USE AND WILDLIFE OPENINGS IN THE EAST GULF COASTAL PLAIN ABSTRACT Wildlife openings, maintained in early successional stages or planted food plots, are often created with the intention of providing forage for wildlife and hunting opportunities. Many non-target species may benefit from wildlife openings including some declining Neotropical bird species. My objectives were to determine how avian use was related to size, edge length, shape, forest type, and management of openings. I developed an a priori set of hypotheses and corresponding models to examine factors that influenced detection and occupancy of bird species in openings on two study areas in the East Gulf Coastal Plain of Alabama. We found the prior detection model was the best model for most species. Date and temperature also were found to be important sources of variation in detection rates. While probabilities of use by 31 species were not strongly related to any of the characteristics of openings that we measured, opening size, edge length, and management were the most important factors that were related to bird use. Several species exhibited weak positive relationships to larger openings. Edge length relationships varied with species as did management style relationships, although there generally were higher probabilities of use for planted openings. Opening shape and surrounding forest type were not related to bird use. The results of this study can be incorporated into management plans to increase probabilities of use for bird species of 12 interest. INTRODUCTION Wildlife openings, man-made clearings in forest lands, are often created to benefit wildlife and create hunting opportunities. Little is known about the quantitative relationships of wildlife openings to non-target species such as songbirds (Chandler et al. 2009, King et al. 2009), however these species use openings at certain times of the year. There are many characteristics of wildlife openings such as size, shape, edge, surrounding forest type, and management that may affect their use by birds. Openings often range in size from small forest clearings resulting from the removal of a few trees to large open fields over 50 ha. Opening size also may be related to the management intent. For example, when created for hunting mourning doves (Zenaida macroura) or northern bobwhite (Colinus virginianus), openings are usually large (>5ha). For hunting other game species such as white-tailed deer (Odocoileus virginianus) and eastern cottontail (Sylvilagus floridanus), openings are usually made much smaller (e.g., <5 ha) forest openings or food plots. With this range in sizes for openings, it is important to understand how opening size affects non-game bird use and abundance. Non-game forest birds may avoid forest adjacent to large openings. In contrast, early successional and grassland species may require openings larger than some threshold size. Another characteristic of openings that may have an impact on bird use is the length of edge. As an opening becomes larger, the amount of edge increases, and this may have positive or negative effects on use by non-game birds. Some nongame bird species may avoid edges because predation and parasitism on nests may increase. Nest 13 predators often concentrate along forest edges, possibly because of increased density of nests in and around edge habitat (Wilcove 1985, Paton 1994, King et al. 1998). Conversely, other species of birds select forest edge habitat for breeding, therefore, their use of openings is expected to increase as the amount of edge increases. Also, several studies have suggested that brown-headed cowbirds (Molothrus ater) concentrate along edges which may increase the chance of parasitism on nests (Helzer and Jelinski 1999, Moorman et al. 2002, Howell et al. 2007). Thus, brown-headed cowbird use should be positively related to the amount of edge. While predation and parasitism may be negative effects of edge habitat, edges often provide foraging opportunities and escape cover from avian predators, which may attract some forest bird species. Similar to area and edge, the shape of the wildlife openings may be related to their use by several bird species. Openings shapes may range from irregular and oblong to perfectly round. As an opening becomes less round, the ratio of edge length to area increases. Forest bird species may select openings with large edge-to-core ratios because there is more edge habitat for them to use and less non-forested area. Many forest species avoid flying through open habitats and fields (Desrochers and Hannon 1997). Circular openings have the smallest edge-to-core ratio, and openings with large core areas may be more attractive to species that are typically associated with grasslands or early successional habitats. Many birds are associated with certain forest types, so the forest surrounding an opening may affect use by some species. One such species is the brown-headed nuthatch (Sitta pusilla), which is primarily associated with mature pine forests (Conner and Dickson 1997). Therefore, the likelihood that this species would be found within and 14 around an opening surrounded by pine forest would be much greater than one surrounded by hardwoods. While certain species, such as white-tailed deer and mourning dove, are the focus of management actions to create openings, all species, both game and non-game, are affected by mechanical alterations to wildlife openings. Some openings are intensely managed with plowing and planting to cultivate food for wildlife, while others are maintained as early-successional fields with no other management actions. Some planted forbs such as common ragweed (Ambrosia artemisiifolia) and partridge pea (Chamaecrista fasciculate) are selected by game species such as northern bobwhite, and they also can be good foraging habitat for non-game birds (Harper 2007). Wildlife openings are frequently used by migrant bird species, but understanding the relationships between bird use and characteristics of openings is limited. My objectives were to determine how four characteristics of wildlife openings (size, shape, edge, and forest type), along with management actions, are related to avian use. With this information, we may be able to design openings that could potentially benefit desired bird species. I measured probability of use using occupancy analysis (MacKenzie et al. 2002). I developed an a priori set of hypotheses and corresponding models to examine factors that influenced detection and occupancy of wildlife openings on two study areas in the East Gulf Coastal Plain of Alabama. STUDY AREAS AND METHODS The study sites selected for this project were located in southern Alabama in the East Gulf Coastal Plain, Alabama. The first area included Fred T. Stimpson (31.38?N, 87.87?W) and Upper State Sanctuaries (31.56?N, 87.96?W) in Clarke County, Alabama 15 which were 20km apart but managed as a single unit (2,230ha). The second study site, Barbour County Wildlife Management Area (31.99?N 85.46?W, 7,660ha), (Barbour) was located 235km east of the sanctuaries in Barbour and Bullock counties in southeast Alabama. The landcover and habitat management on both study areas were similar. Both areas were primarily upland pine and bottomland hardwood forests. During this study hunting was prohibited in the Sanctuaries, and management included the creation and maintainance of numerous wildlife openings primarily for white-tailed deer and wild turkey. Barbour WMA was open to the public for hunting; therefore, the primary management actions on this area were intended to provide hunting opportunities and habitat for game species. Wildlife openings were prevalent throughout Barbour WMA. Most openings were managed with row crops and seasonal grasses, but some were maintained as early successional habitat. The Alabama Gap Analysis Project Landcover map (Kleiner et al. 2007), which was based on satellite imagery from 1999-2001, was used in combination with aerial photography from 1992 and 2006 to locate wildlife openings within the two study areas. Once openings were identified, the perimeter of each opening was digitized, and area and perimeter were calculated using ArcGis (version 9.1 ESRI, Inc.). The area of the openings ranged from 0.05ha to 30ha. Thirty openings were chosen from each study site using a stratified random sample based on size of the opening. An additional 30 alternate openings were chosen for each study area to replace those openings which could not be used at each site. Alternates were used when ground-truthing indicated that openings had not been maintained or they were swamps or ponds. More accurate estimates of the perimeter (edge length) and area of each selected 16 opening were obtained by mapping the perimeter using handheld Global Positioning System (GPS) and importing these data into ArcGIS. GPS data was also obtained from the area manager of Barbour WMA for wildlife openings that were planted as food plots for game species (A. Pritchett,Alabama Department of Conservation and Natural Resources, unpublished data) Length of edge and area were found to be closely related (R=0.906), therefore, we used a shape index (perimeter/area) to incorporate this relationship (Rshape and area= -0.477, Rshape and edge= -0.622). Point count surveys for birds were conducted no later than 4 hours after sunrise twice during the breeding season (May ? July) within each selected opening. All 60 openings were surveyd in 2008, but in 2009, five sites were not surveyed because the surrounding area had been clearcut or they were flooded. For the smaller openings (50m or less in diameter), the center of the point count was located in the center of the opening. In openings greater than 50m in width, the center of the survey point was located 50m from the forest edge at the widest portion of the opening to include species within the opening as well as in the adjacent forest. All survey points were located at least 250m apart to prevent double counting birds. Each survey consisted of three, four-minute counts performed successively. Each bird that was seen or heard was recorded along with the estimated direction and also the distance band (0-25m, 25-50m, greater than 50m) (modified from Hamel et al. 1996). We recorded date, time, and temperature at the beginning of each survey. During June ? August 2008, habitat data were collected on a 6.25m grid of 49 points within a 25m radius of each survey site (Figure 2.1). At each point on the grid, presence or absence of tree canopy (dominant tree cover), midstory (4m to canopy), 17 shrub layer (2-4m), and ground cover (less than 2m) were recorded using a moosehorn densitometer (Robinson 1947). To establish the majority forest edge type for each opening, the proportion of each forest type present around the opening was estimated visually and assigned to one of three categories: deciduous forest, mixed forest, or coniferous forest. Mixed forest was any forest that was less than 70 percent of pine or hardwood. The management type for each opening was classified as planted or unplanted, planted openings were those that were plowed and planted with row crops or seasonal grasses and unplanted openings were those maintained as early succession habitat without mechanical tillage. For those openings with more than one management type, the most prevalent type was used to label the opening as planted or unplanted. The forest and management type of our openings ranged in size, edge length, and shape (Appendix A). Hypotheses My hypotheses regarding detection included that detection of a species would not vary among sites or surveys (p.). I also hypothesized that detection probability would decline through in the morning (ptenp) because male birds may not sing as frequently as temperature increases (Mayfield 1981, Robbins 1981). Additionally, I hypothesized that detectability would decline through the breeding season (pdate) because males sing more at the beginning of the breeding season when they are choosing and attracting mates (Best 1981, Skirvin 1981). I also hypothesized differences in detection among observers (pobs), because not all observers have the same skills at detecting species by sight and sound (Sauer et al. 1994 and Alldredge et al. 2007). I also hypothesized that observers would share information about the locations of rare species; and, thus detection rates for 18 rare species at their known locations would increase once they had been detected (pmemory). Finally, I hypothesized that once an observer had detected any species at a site, detection rates for that species would increase on subsequent surveys by that observer at that site (pprior detect). My a priori occupancy hypotheses consisted of a set of common models that were applied to all species. Additional hypotheses were included for species with specific habitat requirements, which were based on literature review for each species. The common hypotheses addressed the size, shape, length of edge, forest type and management of openings. The size hypothesis (? size) suggests that species occupancy will differ as the size of the opening increases. The edge hypothesis (? edge) predicts that as the length of edge habitat surrounding an opening (i.e., perimeter) increases species occupancy will be either positively or negatively related. The shape hypothesis (? shape) predicts that as an opening becomes more irregularly shaped (i.e., core area decreases) species occupancy will differ among species. The fourth hypothesis, forest type (? forest) suggests that bird occupancy will differ within openings surrounded by different forest types (deciduous, coniferous, and mixed) with fewer species associated with coniferous forest. I also hypothesized that the effect of forest type would be additive to the effects of other opening characteristics for species that were primarily associated with a single forest type. I believed that since some species have strong associations with certain forest types, this may be an additive affect to their relationships with other opening characteristics. My hypotheses with regard to management type (? management) are related to the intensity of management. I expected openings that were tilled or tilled and planted with row crops or seasonal grasses to be used more frequently by all species because of 19 foraging opportunities than unplanted openings that are maintained as pastures or open fields only. Species-specific hypotheses were based on specific vegetative requirements from literature (Hamel 1992) and were included for those species with certain habitat requirements with regards to ground and shrub cover. I hypothesized that some species would respond to specific habitat structure in addition to opening characteristics. For these species, additional additive models including ground or shrub cover were included (Table 2.2). Analysis I estimated occupancy (? ? probability of use) and detection probability (p) (Mackenzie et al. 2002) for each species that was encountered at least 6 times using models corresponding to each of my a priori hypotheses. Goodness of fit was calculated to test for overdispersion and lack of fit of the models to the data with the chi-squared goodness-of-fit statistic (?) (Mackenzie et al. 2006). To account for any lack of fit in the model sets, QAICc was calculated (Burnham and Anderson 2002). Models with ?QAICc ? 2 were considered best approximating models (Burnham and Anderson 2002). Model weights (wi) were calculated as evidence of the relative support for each model (hypothesis). Estimates of log odds (?s) and unconditional estimates of SEs were calculated for each species from the best approximating models to determine the effects of each habitat characteristic on the probability of use (occupancy) of openings. We used the number of sites surveyed to correct for small sample size. Models with inestimable parameters were removed from the analysis for that species. First, we fit detection models for each species (Table 2.1) with the null occupancy model (?.). Observer and prior detection models were removed if an observer never 20 conducted surveys at a site where a species was known to occur, because observer- specific detection rates could not be estimated. Observers were also removed from prior detection models if they never conducted a survey subsequent to the initial detection of a species at a site. An intercept only model (?.) that estimated only the average probability of use among sites was included for each species for comparison to habitat relationship models. Once the best fit detection models (?QAICc < 2.0) were selected for each species, they were then used in combination with occupancy models (Table 2.2) for each respective species. RESULTS We analyzed 9,271 detections of 75 bird species for both years (Appendix A). black vulture, turkey vulture, and great egret were not used in the analysis, because they were considered transients not making use of the survey sites. There was adequate data for 54 species for the analysis with a total of 9,195 individual detections for those species. We found that the prior detection model was the best approximating detection model for 25 of the 54 species in this analysis (Table 2.3). The date model was the best approximating model for 20 species of birds. For 13 species the temperature model fit best. The observer effects model was a top ranked model for 3 species. For 14 species the null model was included in the top detection models, which suggests that detection rates did not vary among sites for those species. Opening size strongly influenced use of 15 species of birds (Table 2.4). This model was the unequivocal best fit model (?=0) for pattern of use for 5 species. The area model recieved strong support for American crow (Corvus brachyrhynchos, wi = 0.354, 21 ?=2.226?6.713) and barred owl (Strix varia, wi = 0.273, ?=0.506?0.328). American crows were less likely to occur as opening size increased, while barred owls were more likely to occur. Similarly, chipping sparrow (Spizella passerine, wi = 0.193, ?=1.245?0.88), indigo bunting (Passerina cyanea, wi = 0.390, ?=9.255?6.542), and barn swallow (Hirundo rustica, wi = 0.232, ?=1.698?0.979) were more likely to use openings as size increased. The parameter estimates or odds of occurence for most species were not affected or had a slight positive impact from larger openings (Figure 2.2). The length of edge habitat surrounding an opening (i.e., perimeter length) had a strong influence on use by 13 species (Table 2.5). The edge model was the unequivocal best model for the pattern of use for one species, American goldfinch (Spinus tristis, ?=0, wi = 0.183, ?=1.058?0.585). American goldfinch was more likely to occur as the length of edge habitat increased. The odds of use for the majority of the species showed low sensitivity to length of edge with small parameter estimates (Figure 2.3). Those species supporting the edge model varied with species such as black-and-white warbler (Mniotilta varia, ?=-0.673?0.654) being negatively related to increased edge length while other species such as indigo bunting (?=2.907?1.748) having strong positive relationships towards increased edge length. Based on model selection results, shape of an opening had a strong influence on the probability of use of 7 species (?<2, Table 2.6). However, the shape model was the unequivocal best fit for the pattern of use for only one species, Eastern bluebird (Sialia sialis, ?=0, wi = 0.321, ?=-1.115?0.601). Eastern bluebirds were more likely to occur as openings became more round. Parameter estimates for most species were close to zero, therefore the odds of occurrence for those species did not differ much (Figure 2.4). 22 However, for those species showing strong support for the shape model, Kentucky warbler (Oporornis formosus, ?=1.636?0.686) did have strong positive relationships towards irregular shaped openings. Forest type surrounding an opening had a strong influence on probabilities of use by 7 species (Table 2.7). The forest type model was the unequivocal best fit model for only the hairy woodpecker (?=0, wi = 0.313). However, most species showed high variability to forest types (deciduous, coniferous, or mixed forest) surrounding openings (Figure 2.5). Very few species were significantly related to forest type. For those having strong support for the forest model, field sparrow had strong positive relationships only for deciduous forest (?=1.115?1.191). Also, ruby-throated hummingbirds (Archilochus colubris, ?=-19.198?11350) illustrated a strong negative relationship towards pine forest openings. The management style of an opening had a strong influence on use by the greatest number of species. The probability of use for 22 species was affected by management (Table 2.8). The management model was the unequivocal best fit for 9 species (?<2, wi >0.24, Table 3). Two woodpecker species, northern flicker (Colaptes auratus, wi = 0.941, ?=-45.901?5.696) and red-headed woodpecker (Melanerpes erythrocephalus, wi = 0.248, ?=-2.002?0.705), were more likely to occur in unplanted openings. Five species typically associated with forest were more likely to occur within planted openings, American redstart (Setophaga ruticilla, ?=1.985?0.631), northern parula (Parula Americana, ?=2.185?0.817), Swainson?s warbler (Limnothlypis swainsonii, ?=3.031?1.111), wood thrush (?=2.259?0.668), and yellow-throated warbler (Dendroica dominica ?=1.892?0911). Conversely, one forest species, pine warbler (Dendroica pinus, ?=- 23 1.924?0.617), showed a lower probability of occurrence in planted openings. Fish crow (Corvus ossifragus, wi = 0.673, ?=-1.524?0.7) was also more likely to occur in unplanted openings. Overall, the odds of occurrence in relation to opening management varied greatly and the majorities of species had positive parameter estimates and were more likely to occur in planted openings (Figure 2.6). Some species that showed strong support for the management model and are more likely to be found in planted openings include brown-headed cowbird and American goldfinch. Ground cover, a species-specific model, was the best fitting model (?=0) for two species, white-eyed vireo and brown-headed cowbird. White-eyed vireo (Vireo griseus) was found more frequently in openings with little ground cover (wi =0.459, ?=- 1.024?0.497) as was cowbird (wi = 0.417, ?=-0.979?0.406). Another species, yellow- breasted chat (Icteria virens), showed evidence of a negative relationship to ground cover (?=1.533, wi =0.078, ?=-0.372?0.332), though not as strong as white-eyed vireo and brown-headed cowbird. Yellow-breasted chat was also the only species with use related to shrub cover in an opening (?=1.011, wi =0.101, ?=0.509?0.362). The null model was among the top-ranked models for 31 species (?<2.0, Table 2.9). It was the best fit model (?=0, wi >0.43) for the pattern of use of 13 of those species. These species were found within all openings and did not appear to select for certain conditions. DISCUSSION Model selection results were used for the basis of our inferences. While we include estimates of odds ratios, in our analysis and acknowledge that the confidence 24 intervals for many species indicate high imprecision, we relied on our model selection results to identify important relationships between species and opening characteristics. The lack of precision in our estimates may indicate a high degree of variability within our results or unmodeled heterogeneity due to the simplicity of the models we compared. Nonetheless, we feel that our results indicate the strongest relationships within the data, and suggest that more data or less parsimonious models would improve the precision of the estimated relationships, but would not change our conclusions. As expected, prior detection by individual observers influenced our detection rates for certain species. This model suggests that if an observer detects a species at a familiar site, they are more likely to detect that species on subsequent surveys at that site. The date model was also important for many species suggesting that detection rates changed over the breeding season. Date is important because males sing at different frequencies throughout the breeding season (Hamel et al. 1996). As expected from my hypotheses, temperature was also an important factor in detection rates for some species. Lynch (1995) found that later in the day detection rates decreased for birds, which was similar to my temperature hypothesis because typically in the late spring and early summer temperatures increase with time of day. Observer effects, which I felt would be important because of the range of observer skills, was not as important as the other detection variables. Use by many species was influenced by certain attributes of wildlife openings. These species showed more selective habitat associations, and may therefore be affected by habitat alterations. Thus, occupancy could be an indicator that management is benefiting or possibly increasing their populations. If not detected, additional 25 management actions may need to be implemented to ensure those species of interest will occur. At the same time this could be an indication of ecological traps as was found in a study of indigo buntings that showed preference for openings with increased edge habitat where they also experienced lower reproduction rates (Weldon and Haddad 2005). It is important to remember that our site placement of our point counts was used to make inferences about species found associated with openings as well as the surrounding habitat. Therefore, some forest species with relationships with may not have necessarily been located within the opening. Instead, those species may have been found in the adjacent forest edge habitat. I hypothesized that use by some species would be related to opening size, and that the relationship would differ depending upon whether species were typically associated with grasslands, forests, or edges. A similar study examined the size of canopy gaps (0.13-0.5ha) and found more species to be associated with those canopy gaps in comparison to dense forest (Bowen et al. 2007). Also, a study in South Carolina that examined bird use of gaps ranging from 0.06-0.5 ha found more species in larger gaps (0.5 ha, Moorman and Guynn 2001). We found that more species used similar size openings, but our range of opening sizes was much greater (0.5-20 ha). As expected, several species such as indigo bunting, a species typically associated with early successional habitats, selected for large openings. This differs from previous studies that showed indigo buntings had no size preference (Greenberg and Lanham 2001, Chandler et al. 2009). However, some forest species, like downy woodpecker (Picoides pubescens ) unexpectedly showed a positive relationship with opening size. Forest species would not typically be found within openings, and often 26 times avoid areas of fragmentation such as wildlife openings. One study in Canada found that forest species would fly greater distances thru forest cover to avoid openings of any size (Desrochers and Hannon 1997). Some studies have shown the impact of predation may be reduced in large openings in comparison to smaller openings. This may explain why some forest species selected larger openings (Saurez et al. 1997). By contrast, other forest species like Eastern wood-pewee (Contopus virens) selected for smaller openings, which was in keeping with my hypothesis that forest species would be less likely to occur in larger openings. While not a strong relationship, Eastern towhee also was found to not use larger openings as much. As an edge species, they may be deterred from areas such as large wildlife openings, because of the extensive amount of open habitat. On the other hand, some edge species such as brown-headed cowbird and northern cardinal (Cardinalis cardinalis) were shown to select larger openings. Selection of larger openings may be a response of increased foraging opportunities that occur within those openings. Also predation risks may not be as great within larger openings as Saurez et al. suggests (1997) because of the increased amount of core area. I hypothesized that the edge length of an opening would be related to bird use, with early successional species negatively related and forest and edge species positively related to edge habitat. American goldfinch, an early successional species, selected edge habitat which was not expected. This could be because edge habitat provides valuable foraging habitat for them (Anders et al. 1998). Use of openings by the majority of species varied. In one study in South Carolina hooded warblers were found most often during the breeding season in edge habitat 27 (Bowen et al. 2007). Given those results, we would expect hooded warblers to be found more often as edge habitat increases. However, use by hooded warbler and ruby-throated hummingbird, two species that predominately use forest, was unaffected by the length of opening edge. These two species were just as likely to occur in an opening with little edge habitat as an opening with increased perimeter. One reason why there may not be any relationships with those two species is that our study areas were both predominately forested areas and therefore those species may have been prevalent throughout all of the openings. The high variability to edge habitat exhibited by most species encountered within openings may be a response to high predation and parasitism associated with edges (Chalfoun et al. 2002, Fink et al. 2006). Brown-headed cowbirds were not affected by the amount of edge habitat present, which was not expected based on previous studies that suggest cowbirds are associated with edge habitat (Helzer and Jelinski 1999, Moorman et al. 2002, Howell et al. 2007). We believed that because of this association with edge habitat, cowbirds would have a higher probability of use with increased amounts of perimeter. On the other hand, there were also several species showing positive relationships to edge habitat. Often there is an abundance of blackberry bushes along field edges that are beneficial for many species and their fledglings (Anders et al. 1998), which could be why those species, such as red-eyed vireo occur more frequently with increased amounts of edge habitat. Indigo buntings showed similar relationships from those of a previous study with their use being highly related to edge length (Weldon and Haddad 2005). That same study also found that buntings had increased nest predation with increased edge length. 28 Even with increased predation they selected for increased edge length. However, there may be increased foraging in openings with more perimeter, which may be why there are so many species with positive associations to edge length even with possible increased predation risks. As an opening becomes more round, I hypothesized that species use would differ with early successional species positively related to round openings and both edge and forest species negatively related to round openings. Eastern bluebird, an early successional and open habitat species, was more likely to occur in irregularly-shaped openings as opposed to round openings. These birds may be more likely to inhabit openings with more edge and less core habitat because they like open fields where they can perch to watch for prey on the ground such as insects (Hamel 1992). Even though shape was not an important influencing factor for most species, there was a high sensitivity of some species to the shape of an opening. The wood thrush, a forest species, did respond as I had hypothesized. I believed that forest species would not be found in openings with a small edge-to-core ratio but would be much more prevalent within irregularly-shaped openings because there wouldn?t be as much open habitat for those species to fly through. One study in Missouri found that the wood thrush, along with their fledglings, would cross through small openings to get to foraging areas, while larger openings deterred them from dispersing (Anders et al. 1998). Therefore, we felt that they would be found more often around irregularly shaped openings because they were relatively less open. Other forest species also followed my hypotheses, such as the Kentucky warbler and yellow-throated warbler (Dendroica dominica), which were less likely to occur in 29 round openings. These species were more likely to occur in irregularly-shaped openings with more edge habitat available. One study found that linear patches of habitat, as opposed to round patches, had higher densities of nests and higher nest success (Bollinger and Switzer 2002), which could be why these species selected the irregularly shaped openings over round openings. I hypothesized that species use would also differ within openings in different forest types. The forest type surrounding an opening influenced some species, but not to a great extent. The hairy woodpecker was most affected by forest type and selected for mixed forests. Multiple studies have shown that more species are often present within deciduous forests as opposed to coniferous forests (James and Wamer 1982, Johnston and Odum 1956). While we hypothesized that we would find more species in openings within mixed forest because species associated with both forest types might be present, we found similar results as previous studies with more species having highly positive relationships towards openings within deciduous forests. Ruby-throated hummingbird showed this relationship, having the strongest preference with deciduous forests. This relationship was expected because ruby-throated hummingbirds are found to avoid coniferous forests (Hamel 1992). Lastly, I hypothesized that the probability of use by individual species would differ between management practices, with more species found in planted openings. This was the most common factor related to occupancy. As expected, planted openings were selected by most species. Planted openings may provide more foraging and feeding opportunities for these species during a crucial time of their life, the breeding season. Some planted species such as partridge pea and native lespedezas can provide seeds for 30 foraging and also escape cover for many songbirds (Harper 2007). Many forest species, such as Acadian flycatcher and wood thrush selected for planted, heavily managed openings. These species may also be using openings for foraging. Forest species such as these sometimes leave their breeding grounds with fledglings to find better foraging habitat such as field edges (Anders et al. 1998). This could be why those species are found to utilize planted openings more often than unplanted. Also, if these planted openings provide cover habitat, there may be more forest species utilizing the openings because they are less vulnerable to predation. Insectivorous species such as summer tanager and red-eyed vireo may not find planted openings beneficial for foraging, which could be why they do not have strong relationships with planted openings. Anders et al. 1998 found red-eyed vireos in early successional areas and field edges where blackberries were abundant which could also explain why these species are found more often within unplanted openings. They may be utilizing the native berries that are located along field edges and thickets. The additional variables I included for only certain species, ground and shrub cover were indeed important for some species. Both white-eyed vireo and brown-headed cowbird were found selected wildlife openings with less ground cover. For the cowbird this makes sense because they like to forage for insects and seeds and such on bare ground (Hamel 1992). This was not expected for the white-eyed vireo, which tends to be found in more dense areas such as thickets and early successional areas (Hopp et al. 1995). Some species did not respond to any of the characteristics of openings that we measured. These species were considered generalists because the null model was the best 31 supporting model. Thus, we could not detect any selection among openings by these species. Although this may have occurred because we lacked sufficient data for rare species like Bachman?s sparrow (Peucaea aestivalis), a species of greatest conservation concern for Alabama because of low population size (Mirarchi et al. 2004, Sauer et al. 2007, Blancher et al. 2007). While we documented 11 encounters, there was little evidence that this species selected wildlife openings with any specific characteristics. Bachman?s sparrow is associated with open pine and early successional habitat in the coastal plain (Hamel 1992, Dunning 1993); therefore, it is interesting that there were no associations with forest type, or any other characteristic of openings. Another species that is exclusively associated with pine forests, the Brown-headed Nuthatch (Johnston and Odum 1956, Hamel 1992), was encountered 29 times on surveys, and like Bachman?s sparrow, we were unable to detect any association with any of the opening characteristics we measured. For this species and several others where the null model was the best model, there was little evidence that any factors we measured affected their use of openings. One reason we had so few encounters for this species and some other forest birds, may be that they usually avoid open habitats such as wildlife openings. Our study was designed only to examine the relationships between use and opening characteristics and we could not determine how commonly other habitats were used. There may also be additional characteristics of openings that we did not measure or include in our analysis that are related to use by birds. We did not incorporate information about surrounding forest patch size within our study. Therefore the surrounding habitats may have an impact on densities of forest species as well as others. Future research could be done to look at the affects of adjacent forests on our species 32 densities. While there may be some exceptions, several species were found to be generalists in agreement with other studies. Tufted Titmouse (Baeolophus bicolor), a typical habitat generalist (Hamel 1992), was also found to be a generalist species in our study. The titmouse was prevalent throughout all openings with no selection for opening characteristics. Other species showed similar relationships as the titmouse including species such as blue jay (Cyanocitta cristata), Carolina chickadee (Poecile carolinensis), and mourning dove. More species showed sensitivity to the shape and amount of edge habitat present within openings. Therefore, they may benefit from irregularly-shaped openings that have increased amounts of edge habitat. Management was also important, so it may be beneficial for more species to have some openings heavily managed, while still leaving a proportion of openings in early successional habitat. For example, the hooded warbler wasn?t affected by edge but was affected by the management of the openings. These birds may have been more interested in planted openings because of the increased foraging available as opposed to unplanted early successional areas. The amount of food available in those openings may take precedence over the importance of edge habitat for that species. One study found that wildlife openings which are plowed and planted may have more abrupt edges with higher predation rates than shrubby, unmanaged openings would have (Saurez et al. 1997), which is why it may also be important to still have a proportion of unplanted openings available. Two opening characteristics, size and forest type, did not have as much of an impact on probability of use in our study. These factors may not be as important to consider when managing for bird use or higher species 33 richness of openings. We found that in general, wildlife openings were used frequently and appeared to be beneficial for many species of birds?specialists and generalists alike. When managing for birds, it is important to manage for the needs of selective species, because generalists do not have specific habitat requirements. It is important to look at the layout of openings to provide for more species. Obviously, if diversity of birds is desired it may be more beneficial to provide a variety of opening types to support the most species. So, when managing wildlife openings for songbirds, as well as game species, look at the overall matrix of openings available to provide different habitats to benefit the most species. 34 LITERATURE CITED Alldredge, M.W., T.R. 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Forestry Chronicles 23: 222-225. Sauer, J.R., B.G. Peterjohn, and W.A. Link. 1994. Observer differences in the North American Breeding Bird Survey. Auk 111: 50-62. Sauer, J.R., J.E. Hines, and J. Fallon. 2007. The North American Breeding Bird Survey, results and analysis 1966-2006. Version 10.13.2007. USGS Patuxent Wildlife Research Center, Laurel, MD. Skirvin, A.A. 1981. Effect of time of day and time of season on the number of observations and density estimates of breeding birds. Studies in Avian Biology 6: 271-274. Suarez, A.V., K.S. Pfennig, and S.K. Robinson. 1997. Nesting success of a disturbance- dependent songbird on different kinds of edges. Conservation Biology 11: 928- 935. 39 Weldon, A.J. and N.M. Haddad. 2005. The effects of patch shape on Indigo Buntings: evidence for an ecological trap. Ecology 86: 1422-1431. Wilcove, D.S. 1985. Nest predation in forest tracts and the decline of migratory songbirds. Ecology 66: 1211-1214. 40 Table 2.1. Hypotheses and corresponding models for species detection rates for birds on Barbour WMA and Stimpson and Upper State Sanctuaries, Alabama 2008-09. Hypothesis Model Does not vary among sites or surveys p. Varies by temperature ptemp Varies by time of year pdate Varies by observer pobs Varies with shared information on rare species. pmemory Varies with subsequent detections by each observer pprior detect *Only best detection models were then run in combination with occupancy models. 41 Table 2.2. Hypotheses and corresponding models for occupancy rates of birds encountered on Barbour WMA and Stimpson and Upper State Sanctuaries, Alabama 2008-09. Hypothesis Model Opening size affects occupancy rates ? size Length of edge affects occupancy rates ? edge Opening shape affects occupancy rates ? shape Forest type affects occupancy rates ? forest Management style affects occupancy rates The effect of forest type is additive to other opening characteristics1 ? management ? forest+size, ? forest+edge, ? forest+shape Ground cover affects occupancy2 ? ground Shrub cover affects occupancy3 ? shrub Ground and Shrub cover both affect occupancy4 ? ground+shrub 1Species-specific model for: American Redstart, Bachman?s Sparrow, Blue-gray Gnatcatcher, Brown- headed Nuthatch, Blue Grosbeak, Downy Woodpecker, Hairy Woodpecker, Kentucky Warbler, Northern Parula, Pine Warbler, Red-headed Woodpecker 2Species-specific model for: American Goldfinch, Bachman?s Sparrow, Brown-headed Cowbird, Carolina Wren, Chipping Sparrow, Common Yellowthroat, Eastern Towhee, Great-crested Flycatcher, Indigo Bunting, Kentucky Warbler, Northern Mockingbird, Prairie Warbler, White-eyed Vireo, Yellow-breasted Chat 3Species-specific model for: American Goldfinch, American Redstart, Bachman?s Sparrow, Black-and- white Warbler, Blue-gray Gnatcatcher, Brown-headed Cowbird, Blue Grosbeak, Carolina Wren, Chipping Sparrow, Common Yellowthroat, Eastern Bluebird, Eastern Towhee, Hooded Warbler, Indigo Bunting, Kentucky Warbler, Northern Mockingbird, Prairie Warbler, Tufted Titmouse, White-eyed Vireo, Wood Thrush, Yellow-breasted Chat, Yellow-billed Cuckoo 4Species-specific model for: American Goldfinch, Bachman?s Sparrow, Brown-headed Cowbird, Carolina Wren, Chipping Sparrow, Common Yellowthroat, Eastern Towhee, Indigo Bunting, Kentucky Warbler, Prairie Warbler, White-eyed Vireo, Yellow-breasted Chat 42 Table 2.3. Best detection models (?<2.0) for each species of bird1 observed in wildlife openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain of Alabama, 2008-09. For this comparison, detection models were fit with a null model of occupancy ( .). Species with more than one best model appear under multiple models. Model Species pprior detect acadian flycatcher blue-gray gnatcatcher brown-headed cowbird blue jay Carolina chickadee Carolina wren common yellowthroat eastern towhee eastern wood-pewee great-crested flycatcher hooded warbler indigo bunting mourning dove northern bobwhite northern cardinal pileated woodpecker red-eyed vireo red-shouldered hawk summer tanager tufted titmouse white-eyed vireo wood thrush yellow-breasted chat yellow-billed cuckoo yellow-throated vireo pobs blue grosbeak northern parula red-bellied woodpecker pdate American goldfinch American redstart Bachman's sparrow barn swallow brown-headed nuthatch chipping sparrow downy woodpecker fish crow field sparrow hairy woodpecker Kentucky warbler northern mockingbird pine warbler prairie warbler purple martin red-headed woodpecker Swainson's warbler wood thrush yellow-breasted chat yellow-throated warbler ptem p American crow American goldfinch Bachman's sparrow barred owl barn swallow black-and-white warbler brown-headed nuthatch eastern bluebird northern flicker orchard oriole red-headed woodpecker ruby-throated hummingbird wild turkey 43 Table 2.3. Best detection models (?<2.0) for each species of bird1 observed in wildlife openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain of Alabama, 2008-09. For this comparison, detection models were fit with a null model of occupancy ( .). Species with more than one best model appear under multiple models. Model Species p. American goldfinch American redstart Bachman's sparrow barn swallow black-and-white warbler brown-headed nuthatch downy woodpecker northern mockingbird orchard oriole prairie warbler red-headed woodpecker ruby-throated hummingbird wood thrush yellow-throated warbler 44 Table 2.4. The relative importance of the area model (?area) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09. While QAICc, -2*ln(Lik), and Delta are presented for informative purposes, they should not be used for interspecific comparisons. Species Model QAICc -2*ln(Lik) Delta Model Likelihood Model Weight K American crow ?area ptemp 792.243 931.914 0.000 1.000 0.354 4 American goldfinch ?area p. 77.211 70.782 1.432 0.489 0.089 3 Bachman?s sparrow ?area p. 73.232 66.803 1.017 0.601 0.049 3 Bachman?s sparrow ?area ptemp 73.372 64.644 1.157 0.561 0.046 4 Bachman?s sparrow ?area pdate 73.987 65.260 1.773 0.412 0.034 4 barred owl ?area ptemp 82.802 74.075 0.000 1.000 0.273 4 barn swallow ?area p. 124.426 117.997 0.000 1.000 0.232 3 brown-headed nuthatch ?area ptemp 233.769 225.042 0.254 0.881 0.103 4 brown-headed nuthatch ?area pdate 235.133 226.406 1.619 0.445 0.052 4 brown-headed nuthatch ?area p. 235.448 229.019 1.933 0.380 0.045 3 blue grosbeak ?area pobs 205.830 232.203 0.841 0.657 0.214 9 chipping sparrow ?area pdate 164.520 155.793 0.000 1.000 0.193 4 downy woodpecker ?area pdate 423.225 414.497 1.441 0.486 0.154 4 eastern-wood pewee ?area pprior detect 413.267 372.357 1.649 0.438 0.181 15 indigo bunting ?area pprior detect 725.744 681.092 0.000 1.000 0.390 16 northern bobwhite ?area pprior detect 352.032 311.123 1.381 0.501 0.158 15 orchard oriole ?area p. 143.964 137.536 1.205 0.547 0.127 3 45 Table 2.4. The relative importance of the area model (?area) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09. While QAICc, -2*ln(Lik), and Delta are presented for informative purposes, they should not be used for interspecific comparisons. Species Model QAICc -2*ln(Lik) Delta Model Likelihood Model Weight K pine warbler ?area pdate 119.663 473.406 1.966 0.374 0.120 4 wild turkey ?area ptemp 228.819 220.092 1.855 0.396 0.146 4 46 Table 2.5. The relative importance of the edge model (?edge) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09. While QAICc, -2*ln(Lik), and Delta are presented for informative purposes, they should not be used for interspecific comparisons. Species Model QAICc -2*ln(Lik) Delta Model Likelihood Model Weight K American crow ?edge ptemp 793.607 933.536 1.363 0.506 0.179 4 American goldfinch ?edge p. 75.779 69.351 0.000 1.000 0.183 3 American goldfinch ?edge ptemp 77.387 68.659 1.607 0.448 0.082 4 American goldfinch ?edge pdate 77.695 68.968 1.916 0.384 0.070 4 Bachman?s sparrow ?edge p. 72.859 66.430 0.644 0.725 0.059 3 Bachman?s sparrow ?edge ptemp 73.000 64.272 0.785 0.675 0.055 4 Bachman?s sparrow ?edge pdate 73.615 64.888 1.401 0.496 0.040 4 barred owl ?edge ptemp 84.236 75.508 1.433 0.488 0.133 4 barn swallow ?edge p. 125.891 119.462 1.465 0.481 0.112 3 barn swallow ?edge ptemp 126.346 117.619 1.920 0.383 0.089 4 black-and-white warbler ?edge p. 48.316 145.265 1.796 0.407 0.091 3 brown-headed nuthatch ?edge ptemp 234.956 226.229 1.442 0.486 0.057 4 chipping sparrow ?edge pdate 165.438 156.711 0.918 0.632 0.122 4 downy woodpecker ?edge pdate 423.015 414.288 1.231 0.540 0.171 4 eastern bluebird ?edge ptemp 126.277 182.073 1.474 0.478 0.153 4 indigo bunting ?edge pprior detect 726.168 681.517 0.424 0.809 0.316 16 orchard oriole ?edge p. 144.620 138.192 1.861 0.394 0.091 3 47 Table 2.5. The relative importance of the edge model (?edge) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09. While QAICc, -2*ln(Lik), and Delta are presented for informative purposes, they should not be used for interspecific comparisons. Species Model QAICc -2*ln(Lik) Delta Model Likelihood Model Weight K wild turkey ?edge ptemp 228.681 219.954 1.717 0.424 0.156 4 48 Table 2.6. The relative importance of the shape model (?shape) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09. While QAICc, -2*ln(Lik), and Delta are presented for informative purposes, and should not be used for interspecific comparisons. Species Model QAICc -2*ln(Lik) Delta Model Likelihood Model Weight K Bachman?s sparrow ?shape p. 72.560 66.131 0.345 0.841 0.068 3 Bachman?s sparrow ?shape ptemp 72.689 63.961 0.474 0.789 0.064 4 Bachman?s sparrow ?shape pdate 73.318 64.591 1.104 0.576 0.047 4 eastern bluebird ?shape ptemp 124.803 179.789 0.000 1.000 0.321 4 Kentucky warbler ?shape pdate 254.125 416.661 0.612 0.736 0.220 4 red-eyed vireo ?shape pprior detect 822.796 778.144 0.067 0.967 0.313 16 wild turkey ?shape ptemp 228.684 219.956 1.719 0.423 0.156 4 yellow-breasted chat ?shape pdate 403.568 718.846 0.870 0.647 0.108 4 yellow-throated warbler ?shape p. 143.222 136.793 0.823 0.663 0.214 3 49 Table 2.7. The relative importance of the surrounding forest type model (?forest) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09. While QAICc, -2*ln(Lik), and Delta are presented for informative purposes, and should not be used for interspecific comparisons. Species Model QAICc -2*ln(Lik) Delta Model Likelihood Model Weight K barred owl ?forest ptemp 83.242 72.130 0.440 0.803 0.219 5 brown-headed nuthatch ?forest ptemp 234.821 223.710 1.306 0.520 0.061 5 field sparrow ?forest pdate 84.230 73.119 0.976 0.614 0.182 5 hairy woodpecker ?forest pdate 160.929 149.818 0.000 1.000 0.313 5 hairy woodpecker ?forest+shape pdate 161.597 148.012 0.668 0.716 0.224 6 hairy woodpecker ?forest+edge pdate 162.911 149.326 1.981 0.371 0.116 6 Kentucky warbler ?forest+shape pdate 254.284 408.684 0.771 0.680 0.203 6 purple martin ?forest pdate 73.005 61.894 1.035 0.596 0.178 5 ruby-throated hummingbird ?forest p. 165.193 156.466 0.000 1.000 0.488 4 ruby-throated hummingbird ?forest ptemp 166.945 155.834 1.752 0.416 0.203 5 50 Table 2.8. The relative importance of the opening management model (?management) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09. While QAICc, -2*ln(Lik), and Delta are presented for informative purposes, and should not be used for interspecific comparisons. Species Model QAICc -2*ln(Lik) Delta Model Likelihood Model Weight K American goldfinch ?management p. 77.535 71.106 1.755 0.416 0.076 3 American redstart ?management pdate 99.064 348.873 0.000 1.000 0.204 4 American redstart ?management p. 100.242 362.300 1.178 0.555 0.113 3 Bachman?s sparrow ?management p. 74.193 67.764 1.978 0.372 0.030 3 black-and-white warbler ?management p. 48.485 145.851 1.965 0.374 0.084 3 brown-headed cowbird ?management pprior detect 257.978 324.623 1.291 0.524 0.219 14 brown-headed nuthatch ?management ptemp 235.136 226.409 1.621 0.445 0.052 4 downy woodpecker ?management pdate 423.610 414.883 1.827 0.401 0.127 4 fish crow ?management pdate 230.840 222.113 0.000 1.000 0.673 4 field sparrow ?management pdate 83.903 75.175 0.649 0.723 0.214 4 hooded warbler ?management pprior detect 653.035 640.081 0.988 0.610 0.232 16 northern bobwhite ?management pprior detect 351.126 310.217 0.475 0.789 0.248 15 northern flicker ?management ptemp 76.348 67.621 0.000 1.000 0.941 4 northern mockingbird ?management p. 75.773 69.344 0.093 0.954 0.192 3 northern mockingbird ?management pdate 76.097 67.370 0.417 0.812 0.163 4 northern parula ?management pobs 648.469 626.869 0.000 1.000 0.896 9 orchard oriole ?management p. 144.129 137.701 1.370 0.504 0.117 3 51 Table 2.8. The relative importance of the opening management model (?management) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09. While QAICc, -2*ln(Lik), and Delta are presented for informative purposes, and should not be used for interspecific comparisons. Species Model QAICc -2*ln(Lik) Delta Model Likelihood Model Weight K pine warbler ?management pdate 117.696 465.015 0.000 1.000 0.319 4 prairie warbler ?management pdate 225.686 216.959 0.963 0.618 0.086 4 prairie warbler ?management p. 226.526 220.098 1.803 0.406 0.057 3 purple martin ?management pdate 72.539 63.811 0.568 0.753 0.224 4 red-headed woodpecker ?management p. 190.396 385.136 0.000 1.000 0.248 3 red-headed woodpecker ?management ptemp 191.822 383.308 1.426 0.490 0.122 4 red-headed woodpecker ?management pdate 192.216 384.135 1.820 0.402 0.100 4 Swainson?s warbler ?management pdate 184.792 176.065 0.000 1.000 0.982 4 wood thrush ?management p. 142.208 349.144 0.000 1.000 0.291 3 wood thrush ?management pdate 142.526 344.052 0.318 0.853 0.248 4 yellow-throated warbler ?management p. 142.399 135.970 0.000 1.000 0.324 3 yellow-throated warbler ?management pdate 143.878 135.151 1.480 0.477 0.154 4 52 Table 2.9. The relative importance of the null model (?.) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09. While QAICc, -2*ln(Lik), and Delta are presented for informative purposes, and should not be used for interspecific comparisons. Species Model QAICc -2*ln(Lik) Delta Model Likelihood Model Weight K Acadian flycatcher ?.pprior detect 426.434 482.051 0.000 1.000 0.410 14 Bachman?s sparrow ?. p. 72.214 68.004 0.000 1.000 0.081 2 black-and-white warbler ?. p. 46.519 146.728 0.000 1.000 0.224 2 blue-gray gnatcatcher ?.pprior detect 829.385 792.051 0.000 1.000 0.501 14 brown-headed nuthatch ?. ptemp 233.515 227.086 0.000 1.000 0.117 3 blue grosbeak ?. pobs 204.988 234.642 0.000 1.000 0.326 8 blue jay ?.pprior detect 292.670 641.587 0.000 1.000 0.595 15 Carolina chickadee ?.pprior detect 543.444 506.110 0.000 1.000 0.609 14 Carolina wren ?.pprior detect 788.354 842.594 0.000 1.000 0.508 15 common yellowthroat ?.pprior detect 414.246 373.337 0.000 1.000 0.347 15 downy woodpecker ?. pdate 421.784 415.355 0.000 1.000 0.316 3 eastern towhee ?.pprior detect 417.267 379.934 0.000 1.000 0.439 14 eastern wood-pewee ?.pprior detect 411.617 374.284 0.000 1.000 0.412 14 field sparrow ?. pdate 83.254 76.825 0.000 1.000 0.296 3 great-crested flycatcher ?.pprior detect 466.069 731.380 0.000 1.000 0.449 14 hooded warbler ?.pprior detect 652.047 642.978 0.000 1.000 0.381 15 mourning dove ?.pprior detect 512.783 745.325 0.000 1.000 0.591 15 53 Table 2.9. The relative importance of the null model (?.) as indicated by model likelihood and weights for species found in openings on Barbour Wildlife Management Area and Sanctuaries in the East Gulf Coastal Plain May-July 2008-09. While QAICc, -2*ln(Lik), and Delta are presented for informative purposes, and should not be used for interspecific comparisons. Species Model QAICc -2*ln(Lik) Delta Model Likelihood Model Weight K northern cardinal ?.pprior detect 768.673 756.438 0.000 1.000 0.558 15 orchard oriole ?.p. 142.759 138.548 0.000 1.000 0.231 2 pileated woodpecker ?.pprior detect 509.530 472.196 0.000 1.000 0.590 14 prairie warbler ?. pdate 224.723 218.294 0.000 1.000 0.140 3 purple martin ?. pdate 71.970 65.542 0.000 1.000 0.298 3 red-bellied woodpecker ?.pobs 652.710 935.299 0.000 1.000 0.486 8 red-eyed vireo ?. pprior detect 822.728 781.819 0.000 1.000 0.323 15 red-shouldered hawk ?.pprior detect 328.393 463.334 0.000 1.000 0.517 13 summer tanager ?.pprior detect 515.770 746.054 0.000 1.000 0.595 15 tufted titmouse ?.pprior detect 827.200 789.867 0.000 1.000 0.537 14 wild turkey ?.ptemp 226.964 220.536 0.000 1.000 0.368 3 yellow-breasted chat ?. pdate 402.698 721.448 0.000 1.000 0.167 3 yellow-billed cuckoo ?.pprior detect 676.653 635.744 0.000 1.000 0.521 15 yellow-throated vireo ?.pprior detect 458.687 428.049 0.000 1.000 0.468 12 54 Figure 2.1Grid used for collecting vegetative structure data. Plot was 25m radius circle around point center with ground and shrub layer measurements made at each 6.25m interval around the plot. 6.25 m 6.25 m 55 Figure 2.2. The relative sensitivity of bird species use to the size of wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain. Parameter estimates are the slopes ( and 95% confidence limits) of the relationship between opening size and the log-odds of occupancy for the size model. Supported models were best approximating models ( < 2.0). Of species encountered in openings, those with positive were more likely to occur as opening size increased. Conversely, species encountered in openings with negative were less likely to occur as opening size increased. 56 Figure 2.3. The relative sensitivity of bird species use to the amount of edge surrounding wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain. Parameter estimates are the slopes ( and 95% confidence limits) of the relationship between opening size and the log-odds of occupancy for the edge model. Supported models were best approximating models ( < 2.0). Of species encountered in openings, those with positive were more likely to occur as opening edge increased. Conversely, species encountered in openings with negative were less likely to occur as opening edge increased. 57 Figure 2.4. The relative sensitivity of bird species use to the shape of wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain. Parameter estimates are the slopes ( and 95% confidence limits) of the relationship between opening shape and the log-odds of occupancy for the size model. Supported models were best approximating models ( < 2.0). Of species encountered in openings, those with positive were more likely to occur as openings became more irregular. Conversely, species encountered in openings with negative were less likely to occur as openings became more round. 58 Figure 2.5a. The relative sensitivity of bird species use to the deciduous forest type surrounding wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain. Parameter estimates are the size ( and 95% confidence limits) of the relationship between deciduous forest and the log-odds of occupancy for the size model. Supported models were best approximating models ( < 2.0). Of species encountered in openings, those with positive were more likely to occur in openings in deciduous forest. Conversely, species encountered in openings with negative were less likely to occur openings in deciduous forest. . 59 Figure 2.5b. The relative sensitivity of bird species use to the mixed forest type surrounding wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain. Parameter estimates are the size ( and 95% confidence limits) of the relationship between mixed forest and the log-odds of occupancy for the size model. Supported models were best approximating models ( < 2.0). Of species encountered in openings, those with positive were more likely to occur in openings in mixed forest. Conversely, species encountered in openings with negative were less likely to occur openings in mixed forest. 60 Figure 2.5c. The relative sensitivity of bird species use to the pine forest type surrounding wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain. Parameter estimates are the size ( and 95% confidence limits) of the relationship between deciduous forest and the log-odds of occupancy for the size model. Supported models were best approximating models ( < 2.0). Of species encountered in openings, those with positive were more likely to occur in openings in pine forest. Conversely, species encountered in openings with negative were less likely to occur openings in pine forest. 61 Figure 2.6. The relative sensitivity of bird species use to the management of wildlife openings on Barbour Wildlife Management Area and the Sanctuaries in the East Gulf Coastal Plain. Parameter estimates are the size ( and 95% confidence limits) of the effect of planting on the log-odds of occupancy. Supported models were best approximating models ( < 2.0). Of species encountered in openings, those with positive were more likely to occur in planted openings. Conversely, species encountered in openings with negative were less likely to occur in planted openings. 62 CHAPTER III: THE RELATIONSHIP BETWEEN AVIAN DENSITY AND WILDLIFE OPENINGS IN THE EAST GULF COASTAL PLAIN ABSTRACT Wildlife openings, maintained in early successional stages or planted food plots, are often created with the intention of providing forage for wildlife and hunting opportunities. Many non-target species benefit from wildlife openings including some declining Neotropical bird species. My objectives were to determine how bird abundance was related to size, edge length, shape, forest type, and management of openings. I developed an a priori set of hypotheses and corresponding models to examine factors that influenced detection and abundance of bird species in openings on two study areas in the East Gulf Coastal Plain of Alabama. We found the prior detection model was the best model for most species. Size, shape and management style were found to be the most important characteristics of openings with the most relationships to bird abundances. Even though size was related to density of more species, the responses we estimated were not large. Abundances of slightly more species were positively related to irregularly- shaped openings as opposed to round openings. Also, more species responded with positive increases in density to planted openings. Forest type and edge were not as strongly related to bird densities. Thirty-four species did not show strong relationships to any of our 5 characteristics. These relationships can be incorporated into management plans to help maintain and possibly increase abundance of species of interest within 63 wildlife openings. INTRODUCTION Wildlife openings, man-made clearings in forest lands that are maintained in early successional stages or planted food plots, are often created with the intention of providing forage for wildlife and hunting opportunities. Many non-target species benefit from wildlife openings (hereafter openings) including some Neotropical bird species whose populations are in decline (Sauer et al. 2007, Blancher et al. 2007). If populations of Neotropical migrants and other songbirds are to benefit from the management of openings, It is important to understand the factors such as size, shape, and vegetation management that influence their use. Size and shape are among the characteristics that could influence the densities of birds using openings. Openings can vary greatly in size from <0.5ha to 50ha fields planted in agricultural crops. Bird species that prefer early successional habitats may select for and be found in higher densities in large regularly-shaped openings used for breeding and foraging. Species associated with forests may occur in greater densities near small, irregularly shaped openings because large openings increase forest fragmentation. The amount of edge habitat also varied greatly among openings. While edge habitat may be used by some species for nesting and foraging, there are negative edge effects on bird populations. Many studies suggest that there may be higher concentrations of predators along edges (Andr?n and Angelstam 1988, Donovan et al. 1997, Chalfoun et al. 2002) because of the increased abundance of nests found there. 64 Also, brown-headed cowbirds (Molothrus ater) have been found in higher numbers along edges. Some studies suggest more nest parasitism occurs along field and forest edges than in other habitats (Donovan et al. 1997, Suarez et al. 1997, Fink et al. 2006, and Chalfoun et al. 2002). We feel the previous findings may be because of increased densities of birds found along edges, which have been found in a study done in Texas (Strelke and Dickson 1980). Therefore bird abundance may be positively related to increased edge length. The size and amount of edge of openings are measured simultaneously using the regularity of their shape?the ratio of perimeter and size. Openings can vary greatly in shape from circular openings with a maximal core area to oblong strips with long perimeters and very little core open area. Oblong openings may be more beneficial to forest species because they avoid flying through forest gaps and openings and instead will fly along the perimeter (Desrochers and Hannon 1997). Thus, forest birds may be more willing to fly across or use the edge habitat along an oblong opening because there is not much open area. On the other hand, round openings with much greater core open habitat than edge habitat may be more beneficial to early successional species that forage and nest within open fields. Also, with less edge habitat surrounding an opening, there may be lower predation and parasitism risks for those species using openings. Therefore, different species may select openings of different shapes. The type of forest surrounding openings can also differ and may influence bird abundance. Openings within deciduous forests may have higher abundances of birds than those openings within pine forests since there are not many species found within pine forests and there are typically low densities of birds found there (Johnston and 65 Odum 1956, James and Wamer 1982). Also, deciduous forests may provide more foraging along edges with fruit bearing trees and bushes such as blackberry (Rubus spp.) which can be found in bottomland hardwoods (Bowen et al. 2007). One study showed there were more nest predators existing along the edge of pine forests (King et al. 1998), which could also reduce the number of birds using openings within them. Openings within mixed forests may have the greatest abundances of forest birds because bird species that use both types of forest may be present. Openings also differ in the management that is implemented within them. Many openings are plowed and planted seasonally to provide food or foraging opportunities for game species. Plantings can range from agricultural crops such as corn (Zea mays) and soybeans (Glycine max), to seasonal grasses and forbs such as lespedezas (Lespedeza spp.) and partridge pea (Chamaecrista fasciculate) (Harper 2007). These planted openings are often used by migratory birds. Some openings are maintained as early successional habitat with mechanical disturbance such as mowing. These openings can benefit bird species greatly by providing annual and biennial grasses and forbs, as well as shrub habitat for foraging, nesting, and escape cover. Bird densities may vary between both types of openings. My objectives were to determine how bird abundance was related to size, edge, shape, forest type, and management of openings. This information could be used by managers to benefit bird populations of conservation concern, like Neotropical migrants. I developed an a priori set of hypotheses and corresponding models to examine factors that influenced detection and abundance of bird species in openings on two study areas in the East Gulf Coastal Plain of Alabama. 66 STUDY AREAS AND METHODS The study sites selected for this project were located in southern Alabama in the East Gulf Coastal Plain, Alabama. The first area included Fred T. Stimpson (31.38?N, 87.87?W) and Upper State Sanctuaries (31.56?N, 87.96?W) in Clarke County, Alabama which were 20km apart but managed as a single unit (two, 2,230ha). The second study site, Barbour County Wildlife Management Area (31.99?N 85.46?W, 7,660ha), (Barbour) was located 235km east of the sanctuaries in Barbour and Bullock counties in southeast Alabama. The landcover and habitat management on both study areas were similar. Both areas were primarily upland pine and bottomland hardwood forests. During this study hunting was prohibited in the Sanctuaries, and management included creating and maintaining numerous openings primarily for white-tailed deer (Odocoileus virginianus) and wild turkey (Meleagris gallopavo). Barbour was open to the public for hunting small and large game animals. Therefore, the primary management actions on this area were intended to provide hunting opportunities and habitat for game species. Openings were prevalent throughout Barbour. The majority of openings were managed with agricultural crops and seasonal grasses, but some were maintained as early successional habitat. Alabama Gap Analysis Project Landcover maps (Kleiner et al. 2007), which were based on satellite imagery from 1991-2001, were used in combination with aerial photography from 1992 and 2006 to locate openings within the two study areas. Once openings were identified, the perimeter of each opening was digitized, and area and perimeter were calculated using ArcGis (version 9.1 ESRI, Inc.). The area of the openings ranged from 0.05ha to 30ha. Thirty openings were chosen from each study site using a stratified random sample based on size of the opening. An additional 30 alternate 67 openings were chosen for each study area to replace those openings that could not be used at each site. Alternates were used when ground truthing indicated that openings had not been maintained or they were swamps or ponds. In 2009, five sites were not surveyed because the surrounding area had been clearcut or they were flooded. More accurate estimates of the perimeter (edge length) and area of each selected opening were obtained by mapping the perimeter using handheld GPS and importing these data into ArcGIS. Also, GPS data was obtained from the area manager of Barbour County Wildlife Management Area for openings that were planted as food plots for game species (A. Pritchett, Alabama Department of Conservation and Natural Resources, unpublished data) Length of edge and area were found to be closely related (R=0.906), therefore, we used a shape index (perimeter/area) to incorporate this relationship (Rshape and area= -0.477, Rshape and edge= -0.622). Point count surveys for birds were conducted within each selected opening twice during the breeding season (May-July) no later than four hours after sunrise. For the smaller openings (50m or less in diameter), the center of the point count was located in the center of the opening. In openings greater than 50m in width, the center of the survey point was located 50m from the forest edge at the widest portion of the opening to include species within the opening as well as in the adjacent forest. All survey points were at least 250m apart to prevent double-counting birds. Each survey consisted of three four minute counts during which each bird that was seen or heard was recorded along with the estimated direction and distance band (0-25m, 25-50m, greater than 50m) (Hamel et al. 1996). At the beginning of each survey, the temperature was recorded (?C) along with the date and time the count began. 68 During June ? August 2008, habitat information was collected on a 6.25m grid of 49 points within 25m radius of each survey site (Figure 3.1). At each point on the grid, presence or absence of tree canopy (dominant tree cover), midstory (4m to canopy), shrub layer (two-4m), and ground cover (less than 2m) were recorded using a moosehorn densitometer (Robinson 1947). To establish the majority forest edge type for each opening, the proportion of each forest type present around the opening was estimated visually and assigned to one of three categories: deciduous forest, mixed forest, or coniferous forest. Mixed forest was any forest that had less than 70 percent of pine or hardwood. The management type for each opening was classified as planted or unplanted, where planted openings were those that were plowed and planted with agricultural crops or seasonal grasses and unplanted openings were those that were maintained as early succession habitat without mechanical tillage. For those openings with more than one management type, the opening was assigned to the cover present in the greatest proportion. The forest and management type of our openings ranged in size, edge length, and shape (Appendix A). Hypotheses My hypotheses regarding detection included that detection of a species would not vary among sites or surveys (p.). I also hypothesized that detection probability would decline through the morning (ptemp) because male birds may not sing as frequently as temperature increases (Mayfield 1981, Robbins 1981). Additionally, I hypothesized that detectability would decline through the breeding season (pdate) because males sing more at the beginning of the breeding season when they are choosing and attracting mates (Best 1981, Skirvin 1981). I also hypothesized differences in detection among observers 69 (pobs), because not all observers have the same skills at detecting species by sight and sound (Sauer et al. 1994 and Alldredge et al. 2007). I also hypothesized that observers would share information about the locations of rare species; and, thus detection rates for rare species would increase after they had been detected. Finally, I hypothesized that once an observer had detected any species at a site, detection rates for that species would increase on subsequent surveys by that observer at that site. After I determined the best detection models for each species, I compared abundance models. My a priori abundance hypotheses included a set of common models that were evaluated for each species. The common hypotheses addressed the size, shape, perimeter length, forest type and management of openings. The size hypothesis (? size) suggested that species abundance would differ as the size of the opening increased. The edge hypothesis (?edge) predicted that as the perimeter length of an opening (i.e., edge) increased species abundance would vary. The shape hypothesis (? shape) predicted that as an opening became more irregularly shaped (i.e., core area decreases) species abundance would differ. The fourth hypothesis, forest type (? forest) suggested that bird abundance would differ among openings surrounded by different forest types (deciduous, coniferous, and mixed) and fewer species would be associated with coniferous forest. My hypotheses with regard to management type (? management) were related to the intensity of management. I expected openings that were tilled or tilled and planted with agricultural crops or seasonal grasses would be used more frequently by more individuals than unplanted openings that are maintained as pastures or open fields. Analysis I estimated abundance (?) and detection probability (p) for each species that was 70 encountered at least 6 times using models corresponding to each of my a priori hypotheses. N-mixture models were used to estimate density as well as detection rates from repeated counts data (Royle 2004). Models with a ?AICc value less than two were considered best approximating models (Burnham and Anderson 2002). Model weights (wi ) were calculated as evidence of the relative support for each model (hypothesis). Estimates of the log rate of change in abundance and unconditional estimates of standard errors (SEs) were calculated from the best approximating models for each species to determine the relationships of each habitat characteristic of openings with abundance of each species. We used the number of sites surveyed to correct for small sample size. Models with inestimable parameters were removed from the analysis for that species. First, for each species all detection models (Table 3.1) were run with the mean abundance model (?.). Observer and prior detection models were removed from a species if an observer never conducted surveys at a site where a species was known to occur because observer-specific detection rates could not be estimated. Individual Observers were also removed from prior detection models if they never conducted a survey subsequent to the initial detection of a species at a site. The best detection models were then used in combination with the abundance models (Table 3.2) for each respective species. RESULTS Bird surveys were conducted with a total of 9,271 detections from 75 species for both years. Black vulture, turkey vulture, and great egret were not used in the analysis, because they were considered transients not making use of the survey sites. Therefore, there was adequate data for 54 species for the analysis with a total of 9,195 individual 71 detections for those species. We found that the prior detection model was the best approximating detection model for 29 of the 54 species in this analysis (Table 3.3). The date model was the best approximating model for 12 species of birds (Table 3.3). For 10 species the temperature model fit best. The observer effects model was incorporated into four species? detection probabilities as well. Along with these detection models, for 9 species the intercept only model, which estimated the average detection rate, all sites and surveys for that species, was included in the top detection models. Opening size had a strong association with abundance for 18 species of birds (?