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Why male flycatchers aren't a patch on the old days

Male-collared-flycatcher1CLIMATE CHANGE IS causing the plumage of a small European bird to evolve – overturning natural selection of its face characteristics, a new study has found.

Research into a longterm study population of collared flycatchers (Ficedula albicollis) revealed that its forehead patch size, which influences male reproductive success, declined over 34 years. This was accounted for by rising spring temperatures at the study breeding site on the Baltic island of Gotland, Sweden.

Lars Gustafsson, of the Department of Animal Ecology, Evolutionary Biology Centre at Uppsala University in Sweden, has studied collared flycatchers, a species which breeds in Europe and overwinters in sub-Saharan Africa, since 1980. Professor Gustafsson has collected various data about its plumage, which features a prominent white ornament on the male’s head.

This established ornament trait is used to signal sexual fitness to rival other males: a bigger and brighter ornament attracts mates. But the study, co-authored by Simon Evans from Uppsala University, found a “dramatic reversal” in the evolution of this trait – the patch is having the opposite result.

The study found that highly ornamented males were selectively favoured following cold breeding seasons but selected against following warm breeding seasons. This suggests that climate change could result in many birds becoming less attractive as the patch size gradually gets smaller.

Prof Gustafsson said: “We assessed selection on forehead patch size and used individual level quantitative genetic modelling to infer the evolutionary change in ornamentation.

“The focus on individual level data collection was key to allowing us to partition the observed phenotypic decline in ornament size into its genetic and environmental components.

“These results are thus consistent with adaptive evolution of an ornament in response to climate change.”

The precise mechanism linking the changing local climate to the reversed selection remains unknown, and researchers say more work is needed to understand the long-term genetic shift in ornamentation.

The study is published in the journal Nature Ecology & Evolution.

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