The finding is based on data from eBird, a database containing 10 years' worth of observations from amateur birdwatchers. Since 2002, eBird has collected more than 48 million bird observations from roughly 35,000 contributors.

Allen Hurlbert, assistant professor of biology at the University of North Carolina-Chapel Hill, and his team analyzed when 18 different bird species arrived at various points across their migration journeys, the journal Public Library of Science reports.

"Timing of bird migration is something critical for the overall health of bird species," he said. "They have to time it right so they can balance arriving on breeding grounds after there's no longer a risk of severe winter conditions.

"If they get it wrong, they may die or may not produce as many young. A change in migration could begin to contribute to population decline, putting many species at risk for extinction," a North Carolina statement quoted Hurlbert as saying.

Although eBird only contains a decade of amateur-submitted data, versus several decades of data compiled by select bird observatories, the information it contains provides greater geographic coverage.