Bird Migration Patterns Are Changing—and Climate Change May Be to Blame

Each year birds begin their migration from nesting grounds to overwintering areas as abundant sources of food begin to dwindle. As winter approaches and insects and other resources drop, birds in the Northern Hemisphere will move south. However, two recent studies have shown that a shifting climate may alter bird migration patterns. 

One study published on October 22 in Current Biology found that Richard's pipits (Anthus richardi) are migrating on an east to west axis instead of heading south towards warmer latitudes, reports Jake Buehler for Science News. The bird usually breeds in Siberia and overwinters in Southern Asia. Althoug, the bird has become a common sight in southern Europe in recent years, sighting were sporadic in the 1980s and '90s. Researchers observing Richard's pipits suspect that a warming climate may have a role in establishing new migratory routes.

A separate study published in Global Change Biology on October 25 analyzed 50 years of bird sighting data. Researchers found some Trans-Saharan migratory birds spend less time in their winter retreats in Africa and more time in their breeding grounds in Europe, reports Mark Waghorn for Study Finds. If this migration pattern continues, birds may no longer need overwinter in Africa at all if they can find food and habitat in Europe year-round. This shift may lead to increased competition for resources between migratory birds and resident birds that never leave their homes, a statement explains.

"The changes in migratory habits we are already seeing could lead to longer breeding seasons for these species, as well as knock-on effects on other species, both here in the UK and in the traditional winter migration destinations," says study first author Kieran Lawrence, a graduate student at Durham University, in a statement.

Richard's Pipits

To track the pipits and find out why they may be moving west instead of south, researchers tagged seven pipits in France during the winter of 2019 to 2020. The following winter, the team recaptured three of the seven birds and analyzed their routes. The data showed that the three birds had flown back to southwestern Siberia for the summer before returning to France, Science News reports.

The team also looked at photographs of 331 pipits in Europe and North Africa from citizen-science databases. The group aged each bird by their appearance and found that vagrant, or birds that fly outside of their range, were always adolescents, per Science News. But the birds migrating west were all adults, and climate change may have rerouted the pipit's migration patterns. Using a computer model comparing weather patterns in Europe between 1961 to 1990 and 1990 to 2018, researchers found that parts of southern Europe are now more suitable wintering locations for birds than in the past. Another factor contributing to the birds' change in route is the urbanization of southern Asian sites the birds previously migrated to. However, the team still needs to investigate this further before confirming.

Besides Richard's pipit, other birds like the yellow-browed warbler (Phylloscopus inornatus) and Siberian chiffchaff (Phylloscopus collybita tristis) have also been spotted migrating west to Europe, which suggests that some migratory birds may be able to adapt to changes in climate, per Science News, but it is crucial to note that not all bird species can adapt. 

Trans-Saharan Migratory Birds

Data from over 50 years from bird sighting retreats in Africa and Spain's South Coast revealed that between 1964 and 2019, European migratory birds—like the willow warbler, garden warbler, and the nightingale—were arriving at their overwintering spots in Africa later in the fall. Come spring, the birds left the region earlier than before as well, reports Patrick Barkham for the Guardian. The find suggests that birds are staying longer in their summer destinations instead of migrating to Africa for more resources and warmer climates because more vegetation is available for longer at their summer locales.

Many birds are currently facing declines in their populations and avoiding the challenging journey to other places may help some of the species survive, the Guardian reports. The team is planning on simulating the new migration patterns to understand how migration patterns may change over time.

Elizabeth Gamillo | | READ MORE

Elizabeth Gamillo is a correspondent for Smithsonian and a science journalist based in Milwaukee, Wisconsin. She has written for Science magazine as their 2018 AAAS Diverse Voices in Science Journalism Intern.