Secretive marsh bird habitat relationships at mid‐continent spring migration stopover sites

Abstract

AbstractDespite several secretive marsh bird (SMB) species being listed as critically imperiled throughout the mid‐continent of North America, limited information on SMB distribution and habitat use within primary migratory corridors results in uncertainty on contributions of wetlands in mid‐latitude states toward their annual cycle needs. Our objectives were to quantify temporal 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, and the resulting habitat conditions during spring migration. We conducted a 2‐year, dynamic occupancy study (2013–2014) that included 6 rounds of repeated call‐back surveys to detect the presence of 5 SMB species (i.e., Virginia rail [Rallus limicola], sora [Porzana carolina], king rail [R. elegans], least bittern [Ixobrychus exilis], and American bittern [Botaurus lentiginosus]) during spring (Apr–Jun) on 107 wetlands across 8 conservation areas and 4 national wildlife refuges throughout Missouri, USA. We detected sora most frequently, followed by least bittern, American bittern, Virginia rail, and king rail. Coefficient estimates indicated colonization probability for all species was positively associated with emergent vegetation cover and negatively associated with amount of open water. Open water was the only variable in the best supported model explaining 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.