North America's bird population is in a swan dive.
The number of birds across the continent has fallen by about 2.9 billion since 1970, experts estimate in a report published Thursday in Science. That's about a 30 percent reduction in their populations, marking what National Audubon Society President David Yarnold is calling a "a full-blown crisis."
Ornithologists' first reliable estimates of bird populations begin in 1970, and stem from volunteer surveys of amateur birdwatchers, The New York Times writes. Researchers used that data to estimate 529 bird species populations between 2006 and 2015, finding a remarkable decline largely among the most common species of birds across North America. In fact, 90 percent of the loss seems to come from dramatic reductions in finches, sparrows, warblers, and other everyday species.
A bit of ornithological good news did come out of the survey: Waterfowl and other wetland birds saw big population growth since the '70s. That's because "recreational waterfowl hunters ... saw to it that conservation programs and policies were put in place," the study's lead author Ken Rosenburg tells Scientific American. Other birds weren't so lucky, and saw their numbers drop due to habitat loss, insect-killing pesticides, and other climate change-related causes. And due to their irreplaceable positions in every type of biome, this population drop all essentially guarantees "other parts of the ecosystem are also in decline and degradation," Rosenburg continued.