These birds are changing color due to climate change, scientists report

A study reports how blue tits in the south of France have gradually lost the color of their plumage in the space of 15 years. A direct consequence of global warming, according to the French scientists who led this research.

Published in the journal, The American Naturalist, the study was carried out between 2005 and 2019 in the south of France by scientists from the UPV/EHU-University of the Basque Country and the Centre d'écologie fonctionnelle et évolutive (CEFE-CNRS) in Montpellier. The study focused on two populations of blue tits -- one living on the outskirts of Montpellier, and the other in the northwest of Corsica.

These small passerine birds are characterized by their blue crest and their yellow breast. But, over the course of their 15-year observation, the scientists noted a clear decrease in coloration in the two populations of birds studied.

A change that the authors of the research associate directly with climate change. "The change in plumage color 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," explains David López-Idiáquez, the study's lead author and researcher in the UPV/EHU's Department of Plant Biology and Ecology.

These changes have not only aesthetic consequences, warns the scientist, as they can also disturb the mating patterns of these birds." In these birds, traits such as coloring function as signals to indicate to other individuals the quality of the specimen, which are decisive, for example, when it comes to breeding," explains the researcher.

The blue tit is not the only animal species experiencing a shift in physiology as a result of climate change. In particular, research published in April 2021 showed that milder spring temperatures and earlier snowmelt could contribute to a reduction in the body size of mountain bees.

To better regulate their internal temperature and adapt to climatic variations, other animals modify the morphology of their ears or their beaks, for example, as is the case of Australian parrots or bats.