Climate change is disrupting bird migration, according to new research. Birds wait longer to migrate in the spring and try to fly faster to complete the migration in less time.
And it’s not only exhausting the birds, it’s also reducing their chances of survival.
Researchers looked at more than 30 years of migration data for a single bird species and analyzed how migration patterns changed over time.
“We found that our research species, the American redstart, delayed its departure from its wintering grounds in Jamaica by up to 10 days, and then moved up to 43% faster to reach its breeding grounds,” said the study’s lead author. Bryant Dossman, the author, said in press release on Tuesday. “However, the increased movement speed also led to a drop in overall survival of more than 6%.”
Dossman, now a postdoctoral fellow at Georgetown University, led the research as a graduate student at Cornell University.
How climate change will affect seasonally-patterned animal behavior is one of the big questions researchers have been trying to answer over the past few decades.
Many species of birds undergo seasonal migrations, flying long distances to escape the cold or to join other species of the same species at certain times of the year on their breeding grounds.
Birds don’t strictly have calendars, so part of the way they know when to migrate is through environmental cues, such as temperature, plant cycles, and other indicators of seasonal change.
However, climate change is causing rapid changes in many of these indicators, making it difficult to know when birds are migrating.
In the peer-reviewed study, published last December, journal ecologyresearchers examined 33 years of migration data for the American redstart, a small bird that breeds in North America, including Canada and the eastern United States, and winters in parts of Central and South America.
Male American Redstarts are black with orange patches, while females have gray heads and yellow patches.
The researchers compared the Red Start’s expected migration departure dates with actual departure dates in recent years to see how it evolved over time.
They found that birds compensated for the effects of climate change, delaying departure dates and completing migrations in a shorter period of time.
“The behavioral changes documented in this study serve as a reminder that the effects of climate change on animals are subtle and, in some cases, detectable only after long-term studies,” Cornell Labs said. The study and paper co-authors said in a press release.
One reason the Red Starts had to delay the start of their northward migration was that Jamaica, one of their main places to stay for the winter, had dried out in recent decades due to climate change. That’s it. That means redstarts eat fewer insects and are not ready to leave for migration at normal times. need more time for
At the same time, the breeding grounds they head north flower once a year earlier, and insects emerge earlier accordingly.
“On average, migratory songbirds live only a year or two, so it’s important to stick to a tight schedule. They only get one or two breeding chances,” Dosman said. “Birds that live longer are less likely to risk early migration because they breed throughout their lives and have more opportunities to pass on their genes.”
Data showed that if migratory birds were delayed by 10 days, they could make up about 60% of the time lost by flying faster and resting less. However, they still arrived late, with a slight increase in mortality as they moved faster, and very few arrived.
“Understanding how animals can compensate is an important part of understanding where the impacts of climate change will be,” said Georgetown University’s Institute for Environment and Sustainability. , senior co-author of the study Peter Marla said in a release. There is a possibility.”
Since this study focused on only one species of bird, it is unclear whether this pattern extends to other species.
The good news, researchers say, is that birds have the flexibility to adapt to a changing world. However, if this trend continues, fewer and fewer redstarts may reach breeding grounds each year.
“First of all, they have some flexibility and variation in behavior, but the question is, have we reached the limits of our ability to respond to climate change?” Dosman said.
