Researchers at Tel Aviv University have found that many birds in Israel have become smaller or longer in the past 70 years, and suggest that this is an adaptation to global warming.
The decrease in body mass of some species and the increase in body length of others increase the ratio of surface area to body volume. These could be strategies to reduce heat as the climate warms, the researchers say.
The research was led by Professors Shai Meiri and Shahar Dubiner of Tel Aviv University’s School of Zoology and the Steinhardt Museum of Natural History. Their paper was published in the scientific journal Global Ecology and Biogeography.
Professor Meiri explains that according to Bergmann’s rule, formulated in the 19th century, birds and animals living in cold climates tend to be larger than similar species living in warmer places.
This is because the ratio of surface area to volume is higher in smaller animals, allowing them to lose more heat (an advantage in warm regions) and vice versa for larger bodies – to minimize heat loss (a benefit in colder climates).
Based on this rule, scientists have recently predicted that global warming will lead to a reduction in the size of animals, with the exception of birds that live near humans such as pigeons and hooded crows – which have access to a good food source and the ability to grow in size in the future (this is what happens to many jackals and wolves that eat things that humans have discarded).
The researchers used the Steinhardt Museum’s vast bird collection to look for changes in bird morphology over the past 70 years in Israel.
They examined nearly 8,000 adult specimens from 106 different species, including migratory birds that pass through Israel every year (such as the common chiffchaff, white stork and black buzzard), and wild birds. habitats (among them Eurasian jays, Eurasian eagles, and partridges), and birds that live near humans.
They built a complex statistical model to evaluate the morphological changes in the birds’ body mass, body length and wing length.
“Our findings suggest that this is an incredibly complex picture,” says Dubiner.
“We identified two different types of morphological changes. Some species became lighter – their mass decreased while their body length remained unchanged – while others became longer. Length. Their bodies have increased, while their mass remains unchanged.
These changes were found in more than half of the species examined, but there was practically no overlap between the two adaptations.
“Hardly any bird species changes towards being both lighter and longer.”
Dubiner continued: “We think these are two different strategies to deal with the same problem, which is rising ambient temperatures. In both cases, the surface area to volume ratio changes. will help the body radiate heat to the environment better. This change is observed throughout Israel and is independent of species or diet.”
Changes in body length tend to be more common in migratory birds, while changes in body mass are more typical in non-migratory birds, Dubiner said.
He added: “The fact that such changes are found in migratory birds from Asia, Europe and Africa suggests that we are witnessing a global phenomenon.”
“Our findings indicate that global warming causes rapid and significant changes in bird morphology.” But what is the impact of these changes? Should we care? Is this a problem, or rather an encouraging ability to adapt to a changing environment?
“Such morphological changes over several decades are probably not evolutionary adaptations, but a certain phenotypic flexibility of the bird,” he said.
“We are concerned that in such a short time the limit on the versatility or evolutionary potential of these traits and birds may be reached and they will not be able to find effective solutions. to adapt as temperatures continue to rise”.