Occupancy and Detection Probabilities of Secretive Marsh Birds in the Kissimmee Chain of Lakes, Florida

Abstract

Loss of marsh habitat has led to population declines of many species of North American marsh birds. However, due to the secretive nature of many of these species there is uncertainty about their population. Recently developed techniques such as the North American Marsh Bird Monitoring Protocol (NAMBMP) and occupancy analysis can be used to improve both the quality and quantity of information we have about secretive marsh birds. In 2009 and 2010, we conducted point counts of black rail (Laterallus jamaicensis), least bittern (Ixobrychus exilis), king rail (Rallus elegans), purple gallinule (Porphyrio martinica), and limpkin (Aramus guarauna) using the NAMBMP in the Kissimmee Chain of Lakes, Florida. We investigate the factors influencing detection and occupancy probability using competing robust design occupancy models in program MARK. We found that detection probability varied with temperature and Julian day for least bitterns, cloud cover and Julian day for purple gallinule, survey location for limpkin, and vegetation cover and detections at the previous point sampled for king rails. Occupancy probability varied with vegetation height for least bitterns, floating vegetation for purple gallinules, vegetation density for limpkins and vegetation density and floating tussocks for king rails. Conserving for diverse assemblages of marsh habitats will support the greatest diversity of secretive marsh birds.