Earlier breeding, lower success: does the spatial scale of climatic conditions matter in a migratory passerine bird?

Abstract

Following over 20 years of research on the climatic effects on biodiversity we now have strong evidence that climate change affects phenology, fitness, and distribution ranges of different taxa, including birds. Bird phenology likely responds to changes in local weather. It is also affected by climatic year‐to‐year variations on larger scales. Although such scale‐related effects are common in ecology, most studies analyzing the effects of climate change were accomplished using climatic information on a single spatial scale. In this study, we aimed at determining the scale‐dependent sensitivity of breeding phenology and success to climate change in a migratory passerine bird, the barn swallow (Hirundo rustica). For both annual broods, we investigated effects of local weather (local scale) and the North Atlantic Oscillation (NAO, large scale) on the timing of breeding and breeding success. Consistent with previous studies in migratory birds we found that barn swallows in Eastern Germany bred progressively earlier. At the same time, they showed reduced breeding success over time in response to recent climatic changes. Responses to climatic variation were observed on both local and large climatic scales, but they differed with respect to the ecological process considered. Specifically, we found that the timing of breeding was primarily influenced by large‐scale NAO variations and to a lesser extent by local weather on the breeding grounds. Conversely, climatic conditions on the local scale affected breeding success, exclusively. The observed decrease in breeding success over years is likely a consequence of scale‐related mismatches between climatic conditions during different breeding phases. This provides further evidence that a species' response of earlier breeding may not be enough to cope with climate change. Our results emphasize the importance of considering the response of ecological processes along different climatic scales in order to better understand the complexity of climate change effects on biodiversity.

Does timing of breeding matter less where the grass is greener? Seasonal declines in breeding performance differ between regions in an endangered endemic raptor

“…In a context of climate change and rapidly changing environmental conditions, a preexisting synchrony between the timing of breeding and the availability of key breeding resources (seasonal food peak) may be disrupted leading to biodiversity loss (Visser et al 2004), but more investigation is needed on this topic (e.g. Visser and Both 2005, Reed et al 2013, Grimm et al 2015.…”

Identifying drivers of breeding success in a long‐distance migrant using structural equation modelling

“…Another explanation for non‐existent COEs is that any effects of events and processes during the non‐breeding period might be less importance and thus, masked by the dominating effect of the previous breeding season, conditions during the current breeding season or individual quality (Ockendon et al , Grimm et al ).…”

“…Furthermore, the variability in arrival dates on the breeding ground was generally smaller than the variability in any other dates of the migration schedule, suggesting that all birds arrive on the breeding ground at similar dates. Another explanation for non-existent COEs is that any effects of events and processes during the non-breeding period might be less importance and thus, masked by the dominating effect of the previous breeding season, conditions during the current breeding season or individual quality (Ockendon et al 2013, Grimm et al 2015.…”

Breeding phenology in Rana temporaria. Local variation is due to pond temperature and population size

“…In contrast, breeding swallows (Hirundo rustica) did not respond locally to variation in weather (Grimm et al. ).…”

“…This has received surprisingly little attention but some examples include hibernation penology of a ground squirrel (Urocitellus parryii) (Sheriff et al 2011), an alpine plant (Anthyllis vulneraria) (Kesselring et al 2015), and breeding birds in urban and rural habitat (M€ oller 2015). In contrast, breeding swallows (Hirundo rustica) did not respond locally to variation in weather (Grimm et al 2015).…”