Apr 20, 2026 Bird Declines as Indicators of Environmental Well-Being
Long-term monitoring data indicate that bird populations across the Americas have declined over several decades, with evidence that the pace of decline has increased in recent years. Research increasingly points to broad environmental pressures operating at large scales, particularly land-use changes and climate change. Analyses of population trends suggest that intensive agriculture—through habitat conversion, landscape simplification, and chemical inputs—is strongly associated with accelerating declines, in part by reducing insect abundance.
Hannah Ritchie of Oxford University’s Our World in Data has provided important insights into the role of agriculture and the changes occurring in global ecosystems. Recent analyses of bird population declines in the Americas provide additional evidence of the adverse impacts of agriculture. In a 2026 paper published in Science, three Czech scientists report that bird populations in the United States are declining faster than before, with agriculture and rising temperatures as primary drivers of the declines.
In 2013, Scott Loss, Tom Will and Peter Marra published a paper in Nature Communications reporting that domestic cats in the United States kill 1.3-4.0 billion birds annually. In 2017, a follow-up paper by Loss and Marra reported the negative impact of domestic cats globally. Additional reports on the impact of cats on bird populations in Canada, Australia, China and Europe appeared following the initial paper by Loss et al. However, the recent analysis concludes that rising temperatures and agriculture’s adverse impact on insect populations are the primary drivers of the accelerating decline in bird populations in North America.
The 2026 analysis in Science (see above) analyzed over 1,000 routes from the North American Breeding Bird Survey covering the period 1987 to 2021 to identify hotspots of bird declines and correlate those hotspots with environmental and anthropogenic variables. About half of the 261 bird species analyzed showed significant population declines from 1987 to 2021, and a quarter showed accelerating declines. The hotspots for accelerating bird declines were mainly located in regions with high-intensity agriculture. Agriculture is associated with three challenges for avian livelihood – the removal of habitat by the creation of large areas of crop monocultures and the treatment of those areas with fertilizers and pesticides. Temperature was also a factor in population decline. The most pronounced average decline in bird populations occurred in states that were already hot, such as Florida and Texas.
Meanwhile, research is documenting bird declines in the Amazon basin, but identifying clear reasons for those declines is proving challenging. One factor appears to be a decline in insect populations. In studies in the American tropics, the number of birds trapped in mist nets near Manaus, Brazil, declined, and all 77 species caught in recent collections weighed less than those caught in the 1980s. Insectivores were the hardest hit. Their abundance fell by more than 50%. Elsewhere, in a Panamanian reserve, 70% of resident bird species were less abundant than in the 1970s, and nine species had almost vanished.
In the relatively stable habitat of a tropical rainforest, small variations in conditions can affect insect and dependent bird populations. A model based on historical capture and weather data found that a 10 C increase in temperature led to a 63% reduction in adult bird survival. In addition, research in the Peruvian mountains indicated that both too little and too much rain reduced local insect biomass.
In the same way that miners used canaries to detect dangerous gas concentrations in mines, studies of bird populations in the Americas are providing indicators of collapsing ecosystems. Human health is also affected by the richness of the surrounding avian community. In a 2021 report, the richness of bird species in a region was correlated with human subjective well-being – the more bird species, the greater human life satisfaction.
In the United States, almost 100 million Americans are bird-watchers. This includes people who watch birds in their backyard to those who are committed birders and keep life lists of the birds they have seen. The Big Year, a 2011 comedy, reflects the level of dedication of such a group of birders. The global bird-watching community experienced explosive growth during the COVID-19 pandemic, and digital platforms like Cornell University’s eBird doubled their user bases in more than two dozen countries, including places as diverse as Nicaragua, Vanuatu and Ukraine. In Canada, bird-watching has overtaken gardening as the favorite leisure activity.
Long-term data from across the Americas indicate that declines in bird populations are being driven primarily by large-scale environmental pressures. Intensive agriculture, habitat simplification, chemical inputs, and rising temperatures are associated with reduced insect abundance and less favorable conditions for many bird species. While other contributors, such as domestic cats, play a role, recent analyses suggest that accelerating declines are most closely linked to land use and climate patterns operating at regional and continental scales. Trends in bird populations provide a useful indicator of broader changes in ecosystem functioning with implications for biodiversity and human well-being.