Imperiled sparrows can exhibit high nest survival despite atypical nest site selection in urban saltmarshes

Abstract

Understanding habitat selection and its fitness consequences in remnant populations of birds in fragmented and urbanized habitat may provide guidance to land managers for imperiled species conservation. We studied Saltmarsh Sparrow, Ammospiza caudacuta, and Seaside Sparrow, A. maritima, nest site selection and nest survival at five sites in New York City (NYC) and one site on western Long Island, New York in 2012 and 2013. We compared marsh vegetation and nest structure characteristics between our study sites and other studied sites for these species in the Northeastern United States. Saltmarsh Sparrows in NYC selected nest sites with the tall form of low-elevation marsh grass (at two sites this was above the proportion available), which is atypical for this species, and Seaside Sparrows selected an upland shrub species at one site, possibly to compensate for a lack of tall low-elevation marsh grasses. Daily nest survival at New York sites increased with nest height above the ground for both species, contrary to previous studies for Saltmarsh Sparrows in intact habitat. Mean nest height for both species was found to be taller in NYC than at other studied locations, and NYC sites may have had taller than average vegetation available, indicating that these sparrows may be able to adapt to some changing marsh characteristics. The difference in nest site selection observed in NYC populations from published studies did not appear to have a cost to nest survival in at least one year. Although high-elevation marsh is the optimal habitat restoration target for Saltmarsh Sparrows, it may be difficult to create in small, urbanized marshes, and our results suggest that other approaches may be successful. A mix of substrates and vegetation heights may allow sparrows to exhibit variation in nest site selection and promote nest survival in the face of changing limiting factors.

Keywords

• ammospiza caudacuta
• ammospiza maritima
• biological conservation
• habitat restoration
• habitat selection
• nest site selection
• nest survival
• saltmarsh
• saltmarsh sparrow
• seaside sparrow
• tidal marsh birds
• urban ecosystem