Climate change is fading the colours of birds

Bird communities will be lost in various regions of the world by 2080, while species such as blue Tare already changing colour over the last two decades due to climate change.

Those are the findings of two separate bird studies by British and European researchers, which point to an accelerating biodiversity crisis as the world changes due to human-induced global warming.

Basque and French researchers observed the two populations of blue T in southern France and the island of Corsica between 2005 and 2019 and found, from almost 6,000 observations, that the bird's characteristic blue crest and yellow breast have vanished.

The study focused on two populations of blue T: one living on the outskirts of Montpellier and the other in northwestern Corsica. These small passerine birds are characterized by their blue crest and yellow breast.

But, over the course of their 15-year observation, the scientists noticed a clear decline in colouration in the two populations of birds studied. A change that the authors of the research associate directly with climate change.

"The change in colour of the plumage seems to be the result of a combination of an increase in temperature (1.23ºC) and a decrease in rainfall (0.64 mm), so that climate change would be the potential cause of this difference”, explains David López-Idiáquez, the main author of the study and researcher at the Department of Plant Biology and Ecology of the UPV/EHU.

These changes not only have aesthetic consequences, the scientist warns, but they can also alter the mating patterns of these birds."

In these birds, traits such as colour function as signals to indicate the quality of the specimen to other individuals, which are decisive, for example, at the time of breeding”, explains the researcher.

Breeding blue T were captured every year during the study period, yielding more than 5,800 observational data on colouration and other characteristics.

The international team warns that these changes will have a great impact on the reproduction of the species, which is endangering its existence. The genetic makeup or physical characteristics of animals can change in response to changes in the territory. They can also move or disappear.

Lopez-Idiaquez said it's crucial to emphasize that this change is plastic in nature rather than genetic and is the result of the body adapting to its environment. He added that since the environment is very similar, despite being less hot, the birds could be going through the same change.

In any case, he continued, only four studies of this type have been carried out worldwide, and none of them has been in the Basque Country. More research of this type, not only at the Basque level but also at the national level, in his opinion, would be quite interesting to carry out.

"Since our environment is quite similar, albeit less hot, our birds may be experiencing the same change," David surmised. “In any case, there are only four studies of this type in the world, and none of them has been carried out in the Basque Country; I think it would be very interesting to carry out more research like this, not only at the Basque level. but also nationally," he added.

It may seem like a purely aesthetic change, but it is quite the opposite, as this change in plumage can have an effect on the "mating patterns" of the species. "In these birds, traits such as colour function as signals to indicate the quality of the specimen to other individuals, which are decisive, for example, at the time of breeding," explains David López.

"This study was made possible by continuous monitoring of the two blue tit populations for more than 15 years, which highlights the importance of long-term studies to understand the effects of climate change on the ecosystems around us," he said. .

When there is a variation in the territory, animal populations have 4 options: the first is to undergo a genetic change; the second is to undergo a plastic change (change in physical characteristics without genetic changes); the third is to emigrate; and the last, disappear. "It is important to emphasize that this change is not genetic but plastic, one of the forms of adaptation to new environmental conditions," he pointed out.

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