Changes in bird size, habits and morphology have been associated with 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 young, which has huge implications for the species. Chiffchaffs are laying their eggs 12 days early. Some birds are shrinking in size, while others, like redstarts, are growing.
The researchers pored over data collected since the mid-1960s in Britain and the Netherlands on 60 different species, including the house sparrow, titmouse Common Bunting, Reed Bunting, Bullfinch and Willow Warbler. They focus on how these birds have changed over time in relation to laying times, number of offspring, and morphology.
While research has already linked how passerines get smaller over time at higher temperatures, scientists weren’t sure if this was directly due to heat stress or because rising temperatures make it harder to find food.
Scientists investigated what proportion of the 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 reinforced these effects.
New study on European birds
O study which was published in the journal Proceedings of the National Academy of Sciences last week, found that while more than half of the changes in features are related to rising temperatures, with warming likely the single most important factor driving the changes over the years. , other factors such as urbanization, pollution, habitat loss and more can also affect changes in characteristics.
“For example, climate change has caused chiffchaffs to lay their eggs six days earlier in the last 50 years, but other unknown environmental factors have led to another six days, meaning that in total they now lay their eggs 12 days earlier. than half a year ago. century. does,” said Martijn van de Pol, lead author of the paper from James Cook University in Australia.
Such a huge time shift can cause a mismatch between when the chicks are born and when food is available to them, upsetting the balance of the ecosystem.
On average, up to 57% of the overall change over the past few decades could be related to warming temperatures, according to the study. Approximately 32% of the 60 bird species had changes in body conditions due to temperatures, with an average decrease in size of 0.45% for each increase in centigrade heat. About 86% had changes in laying times and 31% had changes in the number of offspring.
“Garden warblers in the UK have seen a 26% decline in the average number of offspring over the last half century, which is really concerning for the long-term fate of this species,” said Nina McLean, lead researcher at the studio. from the ANU Research School of Biology. “But only half of that reduction, 13%, can be attributed to climate change.”
Not all species are affected in the same way.
Some, like redstart, are clearly increasing their body condition and youth numbers. The researchers speculate that the variation in how much the characteristics of different species are changing is likely due to factors unrelated to temperature.
“The study provides a well-founded explanation of why different species change at such different rates. And it’s not about sensitivity to temperature, it’s about factors other than temperature,” said Shahar Dubiner, an ecologist at Tel Aviv University who was not involved in the study. Dubiner’s research also found dramatic changes in shape and condition. body of more than half of Israel’s bird species, including many that migrate from Europe, such as storks.
Overall, this means that heating is probably the biggest factor driving the trait change, but it’s not the only element at play.
Other adjacent factors may play a more prominent role than previously thought: the question is what are these factors besides temperature and how are they related to temperature rise?
By Sofia Quaglia. Article in English