ECOLOGICAL AND BEHAVIORAL EFFECTS ON THE REPRODUCTIVE SUCCESS OF URBAN NORTHERN CARDINALS

Abstract

Nest predation is the primary source of reproductive failure for songbirds in most ecological systems. Songbird population declines have often been attributed to elevated nest predation rates in areas affected by habitat loss and fragmentation. Habitat patches within large metropolitan areas that have been developed for decades often support diverse populations of songbirds, but variation in reproductive success in these habitats is understudied. In this dissertation, I investigated the drivers of nest predation in a common songbird, the northern cardinal (Cardinalis cardinalis), in small urban forest patches. Nest predation varied with spatial factors on multiple scales, and was related to spatio-temporal patterns of habitat selection and female personality. Cardinals exhibited lower nest success when nesting in patch edges in more developed landscapes, while LiDAR-derived overstory density and number of small ground-to-canopy gaps surrounding nests were positively associated with nest success. Nest sites were overall spatially biased toward patch edges, but early nesting cardinals preferred habitats with low predation risk, and exhibited higher reproductive success than later nesting birds. Cardinals nesting near patch edges faced more intense and prolonged nest predation pressure, but also exhibited bolder personalities, with bolder nest defense positively associated with nest success. Nest failures related to brown-headed cowbird parasitism extended farther from the patch edge than predation events. This dissertation demonstrates that landscape-dependent edge effects on nest predation emerge even among patches within decades-old urbanized areas, and that cardinal behavior plays an important role in generating spatial patterns of nest predation within urban patches.