Shrinking North American bird population is getting worse faster. Experts blame agriculture, warming

"Nearly half of the 261 species studied showed big enough losses in numbers to be statistically significant and more than half of those declining are seeing their losses accelerate since 1987, according to Thursday's journal Science. The study is the first to look at more than the total bird population by examining the trends in their decrease, where they are shrinking the most and what the declines are connected to."

"Not only are we losing birds, we are losing them faster and faster from year to year, said study co-author Marta Jarzyna, an ecologist at Ohio State University. Except for forest birds, almost every group is doing poorly. So we need to ask ourselves a question. How do we protect these groups of birds?"

"The thing is that species extinction, they start with a decline in abundance, Leroy said, adding that the decline is somehow maybe giving a preview of what it could lead to in terms of species extinction. Cornell University conservation scientist Kenneth Rosenberg said the species declining fastest are often considered pests or trash birds, but if our environment cannot support healthy populations of these extreme generalists, that is a very strong indicator."

A comprehensive study examining 261 bird species reveals that billions fewer birds inhabit North American skies compared to previous decades. Nearly half of the species studied experienced statistically significant population losses, with more than half of declining species showing accelerating losses since 1987. The primary drivers are intensive agriculture and warming temperatures. Forest birds represent the main exception to widespread decline. While the fastest-declining species—including European starlings, American crows, grackles, and house sparrows—maintain large enough populations to avoid immediate extinction risk, their decline signals broader environmental degradation. Researchers emphasize that population decline often precedes species extinction, suggesting these trends may foreshadow more severe ecological consequences.

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