title: 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.
authors.affiliation: Behavioral Ecology Research Group Institute of Biology University of Leipzig Leipzig Germany; Department of Conservation Biology UFZ-Helmholtz Centre for Environmental Research Leipzig Germany.
authors.forename: Annegret
authors.initials: A
authors.lastname: Grimm
authors.affiliation: Behavioral Ecology Research Group Institute of Biology University of Leipzig Leipzig Germany; Junior Research Group of Primate Kin Selection Department of Primatology Max Planck Institute for Evolutionary Anthropology Leipzig Germany.
authors.forename: Brigitte M
authors.initials: BM
authors.lastname: Weiß
authors.affiliation: Behavioral Ecology Research Group Institute of Biology University of Leipzig Leipzig Germany; Junior Research Group of Primate Kin Selection Department of Primatology Max Planck Institute for Evolutionary Anthropology Leipzig Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Kulik
authors.affiliation: Department of Conservation Biology UFZ-Helmholtz Centre for Environmental Research Leipzig Germany.
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Mihoub
authors.affiliation: Max Planck Institute for Evolutionary Anthropology Leipzig Germany.
authors.forename: Roger
authors.initials: R
authors.lastname: Mundry
authors.affiliation: Beringungszentrale Hiddensee Greifswald Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Köppen
authors.affiliation: Grüne LIGA Kohrener Land Kohren-Sahlis Germany.
authors.forename: Tomas
authors.initials: T
authors.lastname: Brueckmann
authors.affiliation: Behavioral Ecology Research Group Institute of Biology University of Leipzig Leipzig Germany; Max Planck Institute for Evolutionary Anthropology Leipzig Germany; Department of Anthropology University College London London UK.
authors.forename: Ruth
authors.initials: R
authors.lastname: Thomsen
authors.affiliation: Behavioral Ecology Research Group Institute of Biology University of Leipzig Leipzig Germany; Junior Research Group of Primate Kin Selection Department of Primatology Max Planck Institute for Evolutionary Anthropology Leipzig Germany; German Center for Integrative Biodiversity Research (iDiv) Leipzig Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Widdig
keywords: Barn swallow; Hirundo rustica; NAO; North Atlantic Oscillation; breeding success; climate change; local temperature; phenology; scale sensitivity