Why Are American Kestrels Declining? New Insights from a Continental Study
May 12, 2026By Robyn Bailey, NestWatch Project Leader
Losing Ground
American Kestrels have been experiencing widespread declines since the mid-1960s.
The American Kestrel is a small, cavity-nesting raptor that breeds from Alaska and Northern Canada to the southern tip of South America. It is one of many grassland-nesting species that share a troubling trend: widespread population declines across North America since the mid-1960s. Although kestrels have been studied more than many other grassland birds, scientists still don’t fully understand the causes of their long-term decline.
From 2022 to 2024, NestWatch participated in a study led by a national working group that brought together numerous long-term datasets on American Kestrels from across the United States and Canada. Many of these data sources were made possible by participatory scientists, including contributors to NestWatch, The Peregrine Fund’s American Kestrel Partnership, Breeding Bird Survey, and those who band birds or report encounters with banded birds. By combining these datasets, researchers were able to examine how demographic factors relate to population trends at a continental scale. The results of this multi-institutional collaboration were recently published in the journal Ecosphere and are publicly available.
Population Trend Map for the Breeding Season
This map shows the cumulative change in estimated relative abundance from 2012 through 2022. Red dots indicate decline and blue dots indicate increase. The darker the color, the stronger the trend. Explore the interactive map here.
The study found that the American Kestrel population declined by 29% between 1986 and 2019 (Howell et al. 2026). Over these three decades, the average annual brood size—about 2.84 young, including failed nests—did not show a corresponding decline, though it did vary from year to year. Instead, the authors found that adult survival rates had a stronger influence on population growth than breeding-related factors.
What does this mean for improving population trends in American Kestrels? The findings suggest several challenges that cannot be solved by nest box provisioning alone. Factors likely affecting adult and juvenile survival include declines in arthropod prey, the use of rodenticides, exposure to neonicotinoid insecticides, and predation pressure. These results may also shed light on broader patterns affecting other grassland birds that share habitat with kestrels.
People can help kestrels by installing nest boxes in safe, pesticide-free areas and adding predator guards to protect both incubating adults and their young. Reducing or advocating against the use of rodenticides can also benefit kestrels and other raptors by improving survival rates.
We are grateful to the many NestWatch participants who contributed nesting data on American Kestrels, making this study possible.
Reference:
- Howell, P. E., A. J. Lawson, K. P. Davis, G. S. Zimmerman, O. J. Robinson, M. A. Boggie, M. J. Eaton, F. Abadi, J. L. Brown, J. A. Heath, J. A. Smallwood, K. Steenhof, T. Swem, B. W. Rolek, C. J. W. McClure, J.-F. Therrien, K. E. Miller, and B. A. Millsap. 2026. American kestrel population trends and vital rates at the continental scale. Ecosphere 17(2):e70526. https://doi.org/10.1002/ecs2.70526