Story at a glance

  • Climate change has already warmed the planet, and it’s causing large-scale disruptions in the synchronization of nature’s big events.
  • New research finds that in the continental United States, bird migrations are coming earlier in the season.
  • Warmer temperatures frequently coincided with the earlier migrations, suggesting a link between climate change and the birds’ changing schedules.

Every year billions of birds fly long distances across America in search of warmer climes and food in the fall, and in the spring they return from where they went to breed. But in the continental United States, the timing of this avian exodus is shifting earlier and climate change might be the cause, according to new research

Researchers suspect that warmer temperatures are pushing the birds’ departure schedule earlier in the year, Science News reports.

The study reviewed 24 years of data, including 13 million radar scans, which the researchers used to spot flocks of birds en route, and found that higher temperatures could reliably predict earlier migrations.

“To see changes in timing at continental scales is truly impressive, especially considering the diversity of behaviors and strategies used by the many species the radars capture,” Kyle Horton, ornithologist and study co-author, said in a statement.

The findings can’t pinpoint why warmer temperatures are associated with earlier migrations, but birds use environmental factors, including temperature and day length, to time their arrival with the availability of food and good nesting conditions.

In spring, the study found that, on average, birds set off on their migrations half a day earlier. The biggest change the researchers observed was in the skies above the Montana-Wyoming border, where the migrations were 1.5 days earlier on average. 

The shift was not as noticeable in the fall, perhaps because of variables like storms, which can delay the birds’ departures, and the addition of fledglings to the migration. 

Even small changes in the pace of life at such a large scale can disrupt entire ecosystems — insects that normally would be picked off by incoming flocks instead might be left to pillage local flora unchecked while the birds go hungry.

Species aren’t powerless to adapt to these changes, but, Horton told Science News, “they may not be changing fast enough to keep up with the resources they rely on.”

Published on Dec 21, 2019