Researchers in Israel recently published the results of a study of eight thousand birds. They’ve noticed changes in the bird’s shape or morphology that they claim are because of climate change.

According to a standard rule of body shape, animals living in warm climates are smaller than those of the same species in a colder climate because the larger volume to surface area ratio is better in warmer climates. The hypothesis from this is that animals will become smaller, except those that live near humans.

The researchers studied 106 different species of birds in Israel including wild birds, migratory birds, and birds that have adapted to live near humans. The end result was evidence of a morphological shift – birds had become lighter or bigger but crucially not both. The results were found in birds that came to Israel from around the world, meaning that the shift is not just a local phenomenon but impacts the entire world. According to the researchers: We think that these are two different strategies for coping with the same problem, namely the rising temperatures. In both cases, the surface area to volume ratio is increased… which helps the body lose heat to its environment.

Both changes were noticed in all three categories of birds, though migratory birds generally had the body mass reduction characteristic and non-migratory birds became longer. Contrary to predictions, the human-accustomed birds also had these changes instead of getting bigger as the researchers expected.

These changes were noticed in only a seventy-year period, which means that climate change is impacting birds rapidly. The researchers caution that this does not represent an evolutionary change but flexibility in the phenotype or physical presentation of genes. The researchers do not know if the birds have enough ability to cope with temperatures continuing to rise.

This work was published in the journal Global Ecology and Biogeography with first author Shai Meiri.

More Information

Recent changes in bird morphology – probably due to global warming (EurekAlert)

“Widespread recent changes in morphology of Old World birds, global warming the immediate suspect,” Shahar Dubiner and Shai Meiri, 2022 February 17, Global Ecology and Biogeography