Birds laying eggs earlier due to rising temperatures
Climate change is transforming European birds’ lives, size and habits according to a new study. Changes noticed include chiffchaffs laying their eggs 12 days earlier and garden warblers having 25% fewer chicks.
The researchers looked at British and Dutch data from the last six decades and studied 60 bird species, including the bullfinch, willow warbler, crested tit and house sparrow. They found that, as well as changes to egg-laying cycles and offspring numbers, some of these birds have become smaller and others have become larger.
Passerines, such as blue tits, chiffchaffs and chaffinches, are becoming smaller, but scientists aren’t quite sure why. Possible explanations include heat affecting their growth directly or making it harder for them to find food.
The study, which was published in the Proceedings of the National Academy of Sciences journal, found that rising temperatures can be linked to 57% of overall change and around 32% of bird species experienced body changes. Approximately 31% changed their number of offspring and 86% moved their egg-laying times.
These changes can be detrimental to the ecosystem because if chicks are born too soon, there may not be adequate food available for them.
Rising temperatures may be the main cause of the changes observed in birds, but it’s not the only one. The researchers discovered that pollution, urbanisation and habitat loss also had an effect, but the full picture of the different factors is not yet fully known.
“Climate change caused chiffchaffs to lay their eggs six days earlier over the last 50 years, but other unknown environmental factors led to an additional six days, meaning in total they now lay their eggs 12 days earlier than they did half a century ago”, said lead author Martijn van de Pol of James Cook University in Australia.
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“Chiffchaffs now lay their eggs 12 days earlier than they did half a century ago.” Martijn van de Pol, James Cook University, Australia