Changes in bird size, habits and morphology have been linked to rising temperatures.
Global warming is changing European birds as we know them, according to a study, but it’s not just rising temperatures that are to blame.
Researchers have found that garden warblers, for example, have a quarter fewer chicks, which has huge implications for the species. Warblers lay their eggs 12 days earlier. Some birds shrink in size, while others, such as redstarts, grow taller.
The researchers looked at data collected since the mid-1960s in Britain and the Netherlands on 60 different species, including house sparrows, great tits, reed buntings, bullfinches and willow warblers. . They focus on how these birds have changed over time in terms of their egg-laying schedules, number of offspring, and morphology.
Although research has previously linked the way passerines become smaller over time at higher temperatures, scientists were unsure whether this was directly due to heat stress or because higher temperatures made it more difficult the search for food.
The scientists investigated what proportion of changes over time were related to warming and whether warming affected some species or traits more than others, as well as whether other factors unrelated to temperature enhanced these effects.
New study on European birds
The study, published in the journal Proceedings of the National Academy of Sciences last week, found that while more than half of trait changes are linked to rising temperatures, warming is likely the biggest driver of change. over the years, other factors such as urbanization, pollution, habitat loss, etc. could also affect changes in characteristics.
“For example, climate change has caused chicks to lay their eggs six days earlier for the past 50 years, but other unknown environmental factors have caused six extra days, which means that in total they are now laying their eggs 12 days earlier than six months ago did,” said Martijn van de Pol, lead author of the paper from James Cook University in Australia.
Such a significant weather change can cause a lag between when the chicks hatch and when food is available for them, upsetting the balance of the ecosystem.
On average, up to 57% of global change in recent decades could be linked to warming temperatures, the study said. About 32% of 60 bird species exhibited changes in body condition due to temperature, with an average size decrease of 0.45% for each increase in centigrade heat. About 86% had changes in laying times and 31% had changes in the number of young.
“Garden warblers in the UK have seen a 26% drop in their average number of offspring over the past half century, which is truly worrying for the long-term fate of this species,” said Nina McLean. , the studio’s principal researcher. from the ANU School of Biology Research. “But only half of that reduction, 13%, can be attributed to climate change.”
Not all species are affected in the same way
Some, like the redstart, markedly increase their body condition and the number of young. The researchers speculate that the variation in the evolution of the characteristics of different species is probably due to factors unrelated to temperature.
“The study gives a well-founded explanation of why different species change at such different rates. And it’s not about temperature sensitivity, but about factors other than temperature,” said Shahar Dubiner, ecologist at Tel Aviv University, who was not involved in the study. Dubiner’s research also revealed dramatic changes in the shape and body condition of more than half of Israel’s bird species, many of which migrate from Europe, such as storks.
All in all, this means that heating up is probably the most important factor causing trait change, but it’s not the only thing at play.
Other adjacent factors may play a more important role than previously thought: the question is, what are these factors other than temperature and how are they related to temperature increase?
By Sofia Quaglia. Articles in English