Long-term phenological shifts in migration and breeding-area residency in eastern North American raptors

ABSTRACT Climate change can affect the distribution, abundance, and phenology of organisms globally. Variations in the timing of passage during autumn and spring migration can have consequences at individual and population levels. We assessed whether global climatic indexes and increasing air temperature over a 28 yr period were concurrent with shifts in the autumn migration phenology of 16 eastern North American raptor species. We used count data from 7 eastern North American raptor-migration watch sites and examined whether key species-specific traits such as migration strategy (complete vs. partial and trans-equatorial vs. not), diet specialization, body mass, flight strategy (soaring vs. flapping), and latitude of the northern limit of breeding distribution were associated with a shift in the timing of autumn migration. Our results suggest an overall delay across species in autumn migration passage date of ∼1 day decade−1, which coincided with an increase in temperature across eastern North America. T...