Data from: Factors influencing plasticity in the arrival-breeding interval in a migratory species reacting to climate change

Climate change is profoundly affecting the phenology of many species. In
migratory birds, there is evidence for advances in their arrival time at
the breeding ground and their timing of breeding, yet empirical studies
examining the interdependence between arrival and breeding time are
lacking. Hence, evidence is scarce regarding how breeding time may be
adjusted via the arrival-breeding interval to help local populations adapt
to local conditions or climate change. We used long-term data from an
intensively monitored population of the northern wheatear (Oenanthe
oenanthe) to examine the factors related to the length of 734 separate
arrival-to-breeding events from 549 individual females. From 1993 to 2017
the mean arrival and egg-laying dates advanced by approximately the same
amount (~5-6 days), with considerable between-individual variation in the
arrival-breeding interval. The arrival-breeding interval was shorter for:
(1) individuals that arrived later in the season compared to early
arriving birds, (2) for experienced females compared to first-year
breeders, (3) as spring progressed, and (4) in later years compared to
earlier ones. The influence of these factors was much larger for birds
arriving earlier in the season compared to later arriving birds, with most
effects on variation in the arrival-breeding interval being absent in late
arriving birds. Thus, in this population it appears that the timing of
breeding is not constrained by arrival for early- to mid-arriving birds,
but instead is dependent on local conditions after arrival. For late
arriving birds, however, the timing of breeding appears to be influenced
by arrival constraints. Hence, impacts of climate change on arrival dates
and local conditions are expected to vary for different parts of the
population, with potential negative impacts associated with these factors
likely to differ for early- versus late-arriving birds.