Factors influencing habitat selection, spatial distribution, and site fidelity in a Neotropical migratory bird, the Veery (Catharus fuscescens)

Breeding site selection is vital for a species’ fitness and is a complicated decision in a heterogeneous world. Birds should seek to maximize fitness and assess habitat quality by synthesizing information from many sources. Appropriate settlement responses vary with the spatial and temporal scales as well as the degree to which the environment is predictable. I used a migratory songbird, the Veery (Catharus fuscescens), to explore hypotheses of breeding site selection in response to environmental cues at multiple spatial and temporal scales, accounting for behavior as well as habitat and topographical features. I quantified abundance of arthropods, nest predators, and availability of nesting substrates. Arthropod and predator abundance varied unpredictably in space both within and across breeding seasons. Veeries did not preferentially occupy sites with high abundance of arthropods and/or low abundance of predators. Nest substrate density was not associated with site occupancy. In a second study, I focused on nest selection in response to a wide-ranging nest predator, the Broad-winged Hawk (Buteo platypterus). I hypothesized that Veeries would avoid nesting near broadcast audio cues of the hawk, or alternatively, nest closer to hawk nests in a protective nesting association. Treatment plots did not differ from control plots in multiple measures of occupancy, nests success, or localized nest site characteristics. These results suggest that Veeries cannot make changes in nest site selection changes within their territory to effectively reduce nest predation risk from hawks, likely because the scale at which hawks forage is much larger than Veery territories. The unpredictability of the environment likely leads Veeries to rely on other information to assess habitat quality. My third study focused on personal experience (i.e., nest success) and its influence on breeding site fidelity. I hypothesized that female Veeries would exhibit fidelity to a site if they successfully fledged young but choose a different location if a nest failed. Similarly, I hypothesized that females would choose nest site characteristics associated with prior nest success. I used a long-term dataset of individually marked females to examine site fidelity at multiple spatial and temporal scales. Females exhibited site fidelity within a breeding season, particularly after nest success at moderate scales but not large ones. The win-stay-lose-switch hypothesis was not supported across breeding seasons at any spatial scale. At the nest microhabitat scale, females chose a different nest substrate for nests initiated after a successful nest. This may be an adaptive strategy to prevent predators from forming effective search images for Veery nests, and warrants further research. Personal experience may be inadequate at the relatively small spatial scale of a territory in unpredictable environments. At larger spatial scales, other factors may influence settlement, including terrain features and presence of conspecifics. For my fourth study, I tested several hypotheses regarding the influence of abiotic landscape features (wetlands, roads, slope, aspect, and elevation) and long-term occupancy of potential breeding sites at three spatial scales (site, neighborhood, and region) using ten years of nest data. Veeries nested more frequently than expected in some potential breeding sites, which suggests that the population exhibits fidelity. High spatial autocorrelation suggests that conspecific presence influences occupancy and site preference. Site-wide nest success was not an important factor for long-term site preference. Wetlands and some topographic features were associated with site preference, which suggests that microclimate could factor into breeding site selection. Overall, my findings suggest that nest site selection is complicated in unpredictable environments, and that multiple temporal, spatial, and biotic scales must be considered to appropriately assess breeding site selection in birds. Habitat features alone are not sufficient to predict either occupancy or nest success by a species and behaviors likely act synergistically with habitat features to influence nesting patterns.