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| Global warming has led to earlier spring arrival of migratory birds, but the extent of this advancement
varies greatly among species, and it remains uncertain to what degree these changes are phenotypically
plastic responses or microevolutionary adaptations to changing environmental conditions.We suggest that
sexual selection could help to understand this variation, since early spring arrival of males is favoured by
female choice. Climate change could weaken the strength of natural selection opposing sexual selection for
early migration, which would predict greatest advancement in species with stronger female choice.We test
this hypothesis comparatively by investigating the degree of long-term change in spring passage at two
ringing stations in northern Europe in relation to a synthetic estimate of the strength of female choice,
composed of degree of extra-pair paternity, relative testes size and degree of sexually dichromatic plumage
colouration. We found that species with a stronger index of sexual selection have indeed advanced their
date of spring passage to a greater extent. This relationship was stronger for the changes in the median
passage date of the whole population than for changes in the timing of first-arriving individuals, suggesting
that selection has not only acted on protandrous males. These results suggest that sexual selection may
have an impact on the responses of organisms to climate change, and knowledge of a species’ mating
system might help to inform attempts at predicting these. | |
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