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Climate change has the potential to influence avian population dynamics through nest-fate sensitivity to temperatures during the breeding season. Nest fate also varies across spatially heterogeneous habitat, and changing land uses may independently introduce stressors on reproductive outcome. Identifying the individual and synergistic effects of climate change and land-use change is necessary for understanding the impact of global change on native species. We studied the nest fate of 3 sympatric species breeding in urban habitat in an arid region of the western United States. We monitored nests (n = 371) of American Robin (Turdus migratorius), Mourning Dove (Zenaida macroura), and Black-headed Grosbeak (Pheucticus melanocephalus) over 4 yr on an urban-to-rural gradient and analyzed nest fate in relation to temperatures at the time of egg laying and after eggs hatched. Habitat measurements included nest height and the amounts of canopy cover and impervious surfaces at 3 spatial scales of 20-m, 100-m, and 500-m radii from the nest. Our data most strongly supported models that included temperature deviation after hatching, nest stage, fine-scale canopy cover, and pedestrian traffic. Nest survival increased at slight temperature increases during the nestling stage, which suggests that in a climate-change context, moderate warming in spring temperatures may be beneficial for some breeding birds. Nests were more likely to survive at locations with more canopy cover in a 20-m radius and at sites with more pedestrian traffic, which suggests that increasing cover of native riparian tree canopy at fine scales may enhance habitat quality in multiuse urban reserves. Our results demonstrate that effects of climate change on avian populations must be considered synergistically with land-use and land-cover characteristics of the urban landscape, including tree canopy cover and level of human disturbance.
