Dataset for Estimating eBird Arrival Dates and Temperature Anomalies for American Kestrels

In migratory birds, among- and within-species heterogeneity in response to climate change may be attributed to differences in migration distance and, consequently, environmental cues that affect timing of arrival at breeding grounds. We used eBird observations and a within-species comparative approach to examine whether migration distance (with latitude as a proxy) and climate explain spring arrival dates in a raptor species with a widespread distribution and diverse migration strategies, the American Kestrel Falco sparverius. We found an interactive effect between latitude and spring minimum temperatures on arrival dates, where at lower latitudes (short-distance migrants) kestrels arrived earlier in warmer springs and later in colder springs, but kestrels at higher latitudes (long-distance migrants) showed no association between arrival timing and spring temperatures. Increased snow water equivalent delayed arrival at all latitudes. Results support the hypothesis that short-distance migrants are better able to respond to conditions on the breeding ground than long-distance migrants, suggesting that long-distance migrants may be more vulnerable to shifts in spring conditions that could lead to phenological mismatch.