Abstract
Climate change is having a discernible effect on many biological and ecological processes. Among observed changes, modifications in bird phenology have been widely documented. However, most studies have interpreted phenological shifts as gradual biological adjustments in response to the alteration of the thermal regime. Here we analysed a long-term dataset (1980-2010) of short-distance migratory raptors in five European regions. We revealed that the responses of these birds to climate-induced changes in autumn temperatures are abrupt and synchronous at a continental scale. We found that when the temperatures increased, birds delayed their mean passage date of autumn migration. Such delay, in addition to an earlier spring migration, suggests that a significant warming may induce an extension of the breeding-area residence time of migratory raptors, which may eventually lead to residency.
Highlights
Current global climate change has already caused consistent patterns of change in the phenology and biogeography of numerous species, ranging from plants to vertebrates [1,2]
To assess long-term spatial and temporal changes in the Mean Passage Date (MPD) of the seven species in western Europe, we only calculated one standardised principal component analysis (PCA) (i.e. subtracting the mean and dividing by the standard deviation (SD) to give all parameters the same variation) on the deployed 3-way matrix 31 years x (7 species x 5 sub-regions), which represents the first stage performed in a three-mode PCA [20,21,22]
Long-term changes in air temperatures To evaluate the influence of climate on the phenology of post-breeding migration, we examined long-term changes in autumn and spring temperatures in Western Europe by standardized PCA (Joliffe 1986)
Summary
Current global climate change has already caused consistent patterns of change in the phenology and biogeography of numerous species, ranging from plants to vertebrates [1,2]. The study of long-term phenological changes in raptor postbreeding migration was undertaken using the Mean Passage Date (MPD) [17].
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