A 2026 study published in Science showed that declines in North American bird populations are speeding up year after year in regions with rising temperatures and intensive agriculture. According to the researchers, these accelerating declines were strongly associated with three factors: the heavy use of chemical pesticides and fertilizers, which destroy local insects, wiping out the birds’ main food source; the replacement of native plants and grasslands with massive crop fields, eliminating nesting grounds; and rising temperatures that compound the problem, adding environmental stress to these altered landscapes. The scientists noted strong statistical correlations between agricultural intensity/rising temperatures and faster bird losses, though they stressed that correlation does not strictly prove single-factor causation.

The researchers used data from the North American Breeding Bird Survey, covering more than 261 species in the U.S. and Canada, rather than tracking other variables such as migratory routes or wintering locations. In the U.S., the highest overall net declines in bird numbers occurred in warmer regions such as Florida, Texas and other Southern states. The fastest acceleration of losses, was most prominent in the Midwest, Mid-Atlantic and California.