WASHINGTON (AP) – At least 112 North American bird species have lost more than half their populations in the past 50 years, according to a new report published Thursday.

Among the birds showing the steepest declines are Allen’s hummingbirds, Florida scrub jays, golden-cheeked warblers, tricolored blackbirds and yellow-billed magpies.

“These are the very real consequences if we are unable to conserve and protect the crucial habitats that birds need,” said study co-author Mike Brasher, a senior scientist at the nonprofit Ducks Unlimited.

For several decades, waterfowl stood out as a conservation bright spot with duck populations growing nationwide even as many other groups of birds declined in the U.S. But that trend has reversed, the new data shows.

The total number of dabbling and diving ducks is down about 30 percent from 2017, said Mr. Brasher. Loss of grasslands habitat and a prolonged drought affecting the wetlands of the Great Plains’ prairie pothole region have taken a toll. Among all waterfowl, numbers are down 20 percent since 2014, the report found.

The latest report is a collaboration between several groups including Cornell University, Ducks Unlimited, American Bird Conservancy, National Audubon Society and the American Ornithological Society.

The work draws on survey data from the U.S. Geological Survey, U.S. Fish and Wildlife Service and citizen projects such as Cornell’s eBird. There are some 2,000 bird species in North America. A third of the species examined are rated as high or moderate concern for conservation due to declining numbers, habitat loss or other threats.

These birds “need urgent conservation attention,” said Amanda Rodewald, a study co-author from Cornell, adding that bird survey trends also reveal the health of their habitats.

The report focuses on birds that must breed and feed in specific habitats such as forests, grasslands and coastal regions. Grassland birds including the Bobolink are most at risk.

“For each species that we’re in danger of losing, it’s like pulling an individual thread out of the complex tapestry of life,” said Georgetown University biologist Peter Marra, who was not involved in the new report.

Dr. Marra pointed to key past conservation successes in the U.S.—such as the comebacks of bald eagles, egrets and osprey.

“We know that we can bend the curve back with targeted conservation plans. But we can’t just close our eyes and hope,” he said.