North American Bird Populations Declining at an Accelerating Rate

Billions fewer birds fly through North American skies today than decades ago, and their numbers are shrinking at an increasingly rapid pace, primarily due to the combined effects of intensive agriculture and rising temperatures, according to a new study published in the journal Science.

Significant Losses and Acceleration of Decline

Nearly half of the 261 species studied exhibited statistically significant population losses. Crucially, over half of those species in decline have seen the rate of those losses accelerate since 1987 . This research marks the first comprehensive effort to analyze not just the extent of bird population decline, but likewise the trends, locations, and contributing factors.

“Not only are we losing birds, we are losing them faster and faster year after year,” says study co-author Marta Jarzyna, an ecologist at Ohio State University.

Which Birds are Most Affected?

While the study reveals widespread declines, some species are faring worse than others. The fastest-declining populations include common species like the European starling, American crow, grackle, and house sparrow. However, study lead author Francois Leroy, also an ecologist at Ohio State University, notes that these species are not currently at risk of extinction.

Kenneth Rosenberg, a conservation scientist at Cornell University who was not involved in the study, emphasizes the broader implications: “The species that are declining fastest…are often considered pests or ‘trash birds,’ but if our environment is not able to support healthy populations of these extremely generalist and adaptable, human-tolerant species, that is a very clear indication that the environment is also toxic for people and for other forms of life.”

This research builds upon a 2019 study by Rosenberg that revealed a loss of 3 billion birds in North America since 1970 , though that earlier study did not analyze changes in the *rate* of decline.

Regional Hotspots of Decline

The study identifies three key regions experiencing the most rapid bird population declines: the mid-Atlantic region, the Midwest, and California .

Losses were also more pronounced in southern states like Florida and Texas, which researchers statistically linked to rising temperatures caused by climate change. “It is in the regions where temperatures increase the most that we see the sharpest declines in population,” Jarzyna explains.

The *acceleration* of declines, however, is primarily linked to agricultural practices.

The Role of Agriculture

Researchers found statistical correlations between the accelerating declines and intensive agricultural practices, including heavy fertilizer use, widespread pesticide application, and the expansion of farmland . While the study doesn’t definitively prove causation, it suggests a strong connection.

Leroy explains that the findings mirror similar research conducted in Europe.

Why Bird Declines Matter

Birds play a vital role in maintaining healthy ecosystems. They contribute to pollination, seed dispersal, and pest control. “If they disappear, those functions are lost too,” Jarzyna points out. “So, from the point of view of ecosystem functioning, it is crucial that our birds do not disappear.”

Habitat destruction is a widespread problem, impacting nearly all bird types except for those inhabiting forests.

“Virtually all habitat types…are in decline,” Jarzyna notes. “So we must ask ourselves a question. How do we protect these groups of birds?”