Annual Survival of Birds Captured in a Habitat Island Bordered by the Urban Matrix of Baton Rouge, LA

Abstract

Urban habitat fragments may provide birds the resources necessary to sustain viable populations in close proximity to human settlement. Conversely, urban habitat fragments may also act as ecological traps, where birds are lured into habitats that negatively affect reproduction or survival. In this study, we compared annual survival estimates of six common resident bird species captured at Bluebonnet Swamp, a 41.7-ha forest fragment bordered by the urban matrix of Baton Rouge, LA, with values derived from the Institute for Bird Populations' MAPS program to determine if populations sampled in the habitat fragment demographically deviated from regional baseline estimates. We found that three species captured at Bluebonnet Swamp exhibited survival estimates consistent with regional averages, whereas Cardinalis cardinalis (Northern Cardinal), Toxostoma rufum (Brown Thrasher), and Poecile carolinensis (Carolina Chickadee) survival estimates were lower than baseline. Edge effects associated with a relatively small preserve coupled with disease and semiannual movements in and out of the study area may be influencing Cardinal and Thrasher survival. We recommend that other studies focus on measuring avian demographics within habitat fragments to identify and mitigate factors that limit population sustainability in human-modified landscapes, as relative density alone may not be an appropriate metric for understanding the value of habitat fragments to birds.