Change in blue tits' feather colours due to climate change, suggests new research
A decrease in the striking colour of blue tits' feathers is likely due to the effects of climate change, a new study suggests.
The blue tit is known for its bright feather colours of a blue crest and a yellow breast.
But researchers, who monitored two blue tit populations in France over a more than 15-year period, found a decrease in "brightness and intensity" in the species' colouring during that time period.
They put the change in the birds' plumage colour down to a rise in temperatures and a decrease in rainfall, suggesting climate change is the "potential cause".
The study was conducted by researchers at the UPV/EHU-University of the Basque Country and the Centre d'Écologie Fonctionnelle et Évolutive (CEFE-CNRS) in Montpellier, France between 2005 and 2019.
One of the blue tit populations was located on the outskirts of Montpellier, southern France, and the other in the north west of the island of Corsica.
Researchers gathered more than 5,800 observations on the characteristics and colouring of the species by capturing all breeding blue tits each year in both populations.
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Their results showed that the blue crests and yellow breasts of blue tits in these two populations are on average less colourful now than when the research first began.
David López-Idiáquez, a researcher in the UPV/EHU's Department of Plant Biology and Ecology, said: “Our work suggests that environmental changes, and specifically climate change, could be the main reason why birds such as the blue tit are undergoing a change in their physical features, more specifically in the brightness and intensity of their colouration.
"A negative trend in terms of brightness and intensity of plumage colouration in both sexes and populations has been observed, although in Corsica this change is more associated with climate,” explained Mr López-Idiáquez.
"The change in plumage colour seems to be the result of a combination of a rise in temperature (1.23ºC) and a fall in rainfall (0.64 mm), so climate change would be the potential cause of this difference."
Although this may appear to to be a purely aesthetic change, Mr López-Idiáquez a different colour of plumage may have an effect on the mating patterns of blue tits.
“In these birds, traits such as colouring function as signals to indicate to other individuals the quality of the specimen, which are decisive, for example, when it comes to breeding,” he explained.
When there is a change in environment, animal populations have several options - undergo a genetic change, undergo a physical (plastic) change, migrate or disappear completely.
In the case of the blue tits monitored, he stressed their change was not genetic but "plastic" as a way of adapting to their new environmental conditions.
Mr López-Idiáquez said there are only four studies of this type in the world and none have been carried out in the Basque Country.
He highlighted the importance of long-term studies to "understand the effects of climate change on the ecosystems around us" and called for more research on the subject to be carried out on a national level.