Webb, E.B., E.B. Hill, K.M. Malone and D. Mengel. Use of a dynamic occupancy model to evaluate secretive marsh bird habitat associations at spring migration stopover sites. Journal of Wildlife Management
Despite several secretive marsh bird (SMB) species being listed as “Critically Imperiled” throughout the mid-continent of North America, there is limited information on SMB distribution and habitat use within primary migratory corridors, resulting in uncertainty on contributions of wetlands in mid-latitude states toward SMB annual cycle needs. Our objectives were to quantify patterns of SMB wetland occupancy during spring migration at a mid-latitude state and evaluate the relationships between SMB colonization probability and water-level management practices, as well as the resulting habitat conditions during spring migration. We conducted a two year dynamic occupancy study (2013-2014) that included six rounds of repeated call-back surveys to detect the presence of five SMB species (Virginia rail (Rallus limicola), sora (Porzana carolina), King rail (R. elegans), least bittern (Ixobrychus exilis) and American bittern (Botaurus lentiginosus)) during spring and summer (April-July) on 107 wetlands across 8 Conservation Areas and 4 National Wildlife Refuges throughout Missouri. Sora were detected most frequently, followed by Least Bittern, American Bittern, Virginia Rail, and King Rail. Colonization probability for all species was positively associated with emergent vegetation cover and negatively associated with amount of open water. Open water was the most important factor for American Bittern site colonization, to which they were negatively associated. Virginia Rail colonization had a strong positive association with vegetation height, whereas Least Bittern and Sora site colonization were influenced positively by water depth and agriculture, respectively. Based on the habitat associations within and among SMB species identified in this study, wetland managers can tailor management strategies to optimize spring migration habitat for single- or multi-species objectives.