Spring is Arriving Earlier, Messing With Bird Migrations

Thanks to climate change, spring now comes earlier. But how much sooner the season arrives varies across the U.S. That’s according to a new study that assessed the first appearance of leaves and flowers in nearly 500 U.S. National Wildlife Refuges over more than 100 years.

Researchers found the irregular seasonal changes affect migratory birds’ breeding sites, an outcome that could endanger many species.

Hundreds of migratory birds travel thousands of miles across the U.S. each year. Many birds move from Central America, where they spend the winter, to locations across the northern U.S. to breed and raise young. The success of their international travels depends on good timing. The birds must coordinate their arrivals with spring’s appearance to ensure enough food is available to eat at their destination.

Though some birds have adjusted when they migrate, it’s still unclear whether they’ll be able to keep up with changes in food availability across such vast distances over the long-term.

The researchers mapped data of first leaf and first bloom appearances, indices that mark the onset of spring, across 496 national wildlife refuges in the U.S. stretching back to the beginning of the last century. They found that spring now starts earlier — with leaves budding up to 3 days sooner each decade — in 76 percent of the wildlife refuges.

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