Bobolink (Dolichonyx oryzivorus) site selection is a multiscale process in highly fragmented landscapes
*Meghan C.M. Oliver1 and Joseph J. Nocera1
1Forestry and Environmental Management, University of New Brunswick, Fredericton, NB
Bobolinks (Dolichonyx oryzivorus) rely on nesting habitat created from hayfields and pastures. The species is area-sensitive and their fitness and habitat connectivity are positively correlated. The environmental correlates of breeding site selection have been well-studied, particularly in areas of contiguous habitat (e.g., prairies, extensive agricultural regions). However, much less is known about their breeding site selection in areas of low connectivity and limited habitat choices. We examined Bobolink abundance and nest success in the Wolastoq/Saint John River Valley near Fredericton, New Brunswick. This area represents their northeastern range edge, and the agricultural areas here are highly fragmented and surrounded by a wooded matrix, unlike most areas in the Bobolink's breeding range. In May to July of 2023, we collected abundance and breeding data using point count surveys and a reproductive index at nine sites. We then used geospatial modelling to quantify two patch-level and three landscape-level variables at four different spatial scales. Our modelling suggests that our variables do not predict nest success, further corroborating that haying is the most common cause of nest failure. We found that abundance is predicted by both patch-level variables, as well as metrics of habitat fragmentation and isolation at larger spatial scales, suggesting that Bobolinks are sensitive to fragmentation and may not be driven by habitat amount in these habitat-limited landscapes. Ultimately, the findings from this study can be used to better describe critical nesting habitat and inform management plans for this threatened grassland bird in jurisdictions not dominated by agriculture.
Keywords: agro-ecosystems; conservation; Bobolink; species-at-risk; landscape ecology
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