Urbanization increasingly causes alterations in prey diversity and abundance, land cover, and human disturbance, subsequently impacting populations of even the most adaptable species. American Kestrels are currently considered urban adapters, which may be veiling the influence of urbanization on their continental population decline. We quantified overwintering abundance and sex ratios of American Kestrels throughout the past three decades in a rapidly developing region of the species’ wintering range in southeast Florida to study spatial and temporal population trends relative to degree of urbanization. We detected a significant negative correlation between annual building density and kestrel abundance. Sex ratios also significantly shifted from predominantly female to predominantly male over time and in association with increased residential development. This trend suggests that developed landscapes may represent lower quality territories, as females typically occupy better quality overwintering habitat than males. These results suggest that urbanization may negatively impact overwintering American Kestrel populations in this region and should be investigated as a possible factor contributing to the overall continental population decline, particularly in the eastern flyway where urbanization is prevalent.

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