Factors influencing plasticity in the arrival‐breeding interval in a migratory species reacting to climate change

Abstract

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: (a) individuals that arrived later in the season compared to early‐arriving birds, (b) for experienced females compared to first‐year breeders, (c) as spring progressed, and (d) 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 midarriving 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.

Early Breeding Conditions Followed by Reduced Breeding Success Despite Timely Arrival in an Alpine Migratory Songbird

“…Similar patterns were found in migratory Horned Larks (Eremophila alpestris) that performed long stopovers before reaching their high elevation breeding grounds (de Zwaan et al, 2019). In addition to a general adjustment in the arrival time, wheatears can adjust the arrival-breeding interval according to their arrival dates and spring progression (Low et al, 2019), strongly suggesting that, to some extent, wheatears are able to match their migration and breeding activities with local conditions and seasonally limited resources (Arlt and Pärt, 2017).…”

“…Population-specific migration schedules, such as the later transition of northerly populations (Maggini et al, 2013), and potential trends may thus be hidden in the sightings dataset. In fact, wheatears from Greenland (Oenanthe oenanthe leucorhoa) have advanced their migration within the last three decades (Desaever and Bairlein, 2020) and previous studies on a northern lowland population of the wheatear have shown a continuous trend toward earlier arrival at breeding sites (Low et al, 2019). Constant effort trapping data of wheatears stoppingover on islands in the Mediterranean Sea has revealed a weak, but not significant, trend toward earlier passage during spring migration within the last 18 years (Maggini et al, 2020).…”

Latitudinal variation in arrival and breeding phenology of the pied flycatcher Ficedula hypoleuca using large‐scale citizen science data

“…Upon arrival at breeding territories, after migrating, females are assumed to need to gain condition for egg laying. However, we are aware of no studies of this on small migratory passerines, and so how long this may take and which factors may cause this to vary is unknown (Low et al 2019). In pied flycatchers this may be no longer than the 10 days necessary for the growth of ovaries and oviduct, a process that can start during migration before arrival to breeding grounds (Silverin 1980).…”

Reduced Breeding Success Suggests Trophic Mismatch Despite Timely Arrival in an Alpine Songbird

“…Population speci c migration schedules and potential trends may thus be hidden in the sighting dataset. In fact, wheatears from Greenland (O. o. leucorhoa) have advanced their migration within the last three decades 33 and previous studies on a northern lowland population of the wheatear have shown a continuous trend towards earlier arrival at breeding sites 34 . Constant effort trapping data of wheatears stopping over on islands in the Mediterranean Sea has revealed a weak, but not signi cant, trend towards earlier passage during spring migration within the last 18 years 35 .…”

“…Similar patterns were found in migratory Horned larks (Eremophila alpestris) that performed long stopovers before reaching their high elevation breeding grounds 20 . In addition to a general adjustment in the arrival time, wheatears can adjust the arrival-breeding interval according to their arrival dates and spring progression 34 , strongly suggesting that, to some extent, wheatears are able to match their migration and breeding activities with local conditions and seasonally limited resources 37 .…”