Post‐independence mortality of juveniles is driven by anthropogenic hazards for two passerines in an urban landscape

Urban environments impose novel selection pressures with varying impacts across species and life history stages. The post‐fledging stage for migratory passerines, defined as the period of time from when hatch‐year birds fledge until their first migration, is a poorly understood component of annual productivity that potentially limits population growth. We studied two migratory passerines with positive and negative population responses to urbanization, respectively: Gray Catbird (Dumetella carolinensis) and Wood Thrush (Hylocichla mustelina). Our goals were to estimate post‐fledging survival rates for urban bird populations and determine which features of the urban landscape impact mortality risk during the post‐fledging stage. From 2012–2014, we tracked 127 fledglings (60 Gray Catbirds and 67 Wood Thrushes). Over 55 days after fledging, cumulative survival of Gray Catbirds (0.32 [95% CI: 0.22–0.47]) was approximately half that of Wood Thrushes (0.63 [95% CI: 0.52–0.75]). Thus, survival ...