Marsh bird occupancy dynamics, trends, and conservation in the southern Great Lakes basin: 1996 to 2013

Using data from 21,546 point counts conducted by volunteers in Bird Studies Canada's Great Lakes Marsh Monitoring Program, I assessed whether occupancy of 15 breeding marsh bird species increased or decreased throughout the southern portion of the Great Lakes basin between 1996 and 2013. I accounted for differences in detection probability, addressed spatial autocorrelation, and assessed whether initial occupancy in 1996 and subsequent colonization or extinction at a site within and across species was influenced by site, wetland, and landscape scale covariates. Occupancy of 9 of 15 (60%) species significantly decreased, whereas occupancy of only 1 (7%) species significantly increased. The results show the power of citizen science and suggest that the largest number of decreasing marsh-dependent breeding bird species will benefit from conserving, restoring, or creating large wetlands surrounded by limited urban land use, and from addressing issues within International Joint Commission Areas of Concern. Plus, individual or smaller groups of decreasing species will also benefit from conserving, restoring, or creating robust-emergent-dominated but interspersed, purple loosestrife (Lythrum salicaria)-free, Phragmites-free wetlands surrounded by higher proportions of wetland cover in the surrounding landscape, and from addressing issues within Great Lakes coastal wetlands. These actions will help promote colonization or reduce extinction and help slow or maybe even reverse declining trends in occupancy among decreasing species across the southern portion of the Great Lakes basin.