05 Feb American Kestrels in San Diego
If you have ever been driving down a two lane highway through the grasslands of the US and seen a small, dove-sized raptor perched on a wire, bobbing their head as they scan the fields below or even hovering over a field before plunging into a clump of grass, you have been blessed by the company of an American kestrel. These are beautifully feathered specialized hunters that prey on small birds, rodents and insects, serving an important role in keeping their prey populations in check. In doing so, they are valuable in controlling crop loss, and the spread of disease, due to commons pests. Kestrels belong to the falcon family, with rusty colored plumage, striking black stripes down their cheeks and black flecking, and the males have a striking dusty blue crown and wings.
In recent years, annual American kestrel migration counts have indicated declining populations across North America (HawkWatch International). It’s easy to point the finger at the most obvious answer, and many people do blame insecticides as the 
reason. However, the cause for kestrel population declines is complex, and likely involves a network of several combined factors including habitat loss, insecticides, and competition of invasive species for nesting sites. Data collected from bird counts, migration watch sites and nest box monitoring can help paint a picture to identify factors that are influencing the decline of American kestrel populations.
Nest monitoring
American Kestrels are secondary cavity nesters, which means that they don’t build or excavate their own nests. They often build nests within standing snags, making dead trees particularly important. Projects that aim to monitor nest sites help identify specific issues that influence breeding success in a particular region.
These projects often incorporate volunteer citizens and scientists monitoring natural local nests. Additionally, specially designed nest boxes can be installed in appropriate habitats to provide safe sites designated to increase breeding opportunities. These nest boxes can be easily installed and regularly monitored by volunteers. The more information that can be gathered, the better understanding we have to help this important species thrive.
Implementation in San Diego County
The Avian Behavior Foundation is excited to initiate a Kestrel Monitoring Project to help scientists better understand the breeding habits/distributions of American Kestrels throughout San Diego County. Specific areas with appropriate kestrel habitats will be provided with nest boxes installed ahead of the breeding season. Throughout the breeding season, volunteer monitors will regularly check on the boxes in accordance with our protocols and make notes on the nest box activity.
We are looking for private landowners that are interested in participating in important conservation work for this diminutive falcon.
Are you interested in volunteering for our kestrel project for 2025? Fill out this form to apply for one of our citizen science roles!