The American Kestrel Nest
Box Project Continues
American Kestrel ©Mary Badger
Last April, this column reported on an effort to support populations of the American Kestrel by installation of nest boxes in auspicious spots in Yolo County. The project began in 2023 with ten boxes on select City of Davis properties. It has since grown to thirty-two boxes and the creation of partnerships to extend the reach of the effort. After a successful 2025 breeding season, an update is in order.
The American Kestrel is the smallest North American falcon and the commonest one in Yolo County. It nests in cavities created by other animals or through natural processes like broken tree limbs. American Kestrels hunt a variety of prey, including small mammals, insects, and occasionally small birds. The species is included in two long-term monitoring efforts – the North American Breeding Bird Survey and Christmas Bird Count – that provide insights into trends in its abundance. Unfortunately, kestrel numbers have been declining for years both locally and throughout California, and in many parts of the West. While pesticide use, collisions with motor vehicles, and predation by other birds of prey are implicated in the decline, lack of suitable nest cavities is thought to be a limiting factor in some areas, including Yolo County.
In 2024 and 2025 the project expanded to central, southern, and western Yolo County on lands administered by the Cities of Davis and Woodland, the UC Davis Putah Creek Reserve, and on cooperating private lands. Four more boxes are on the Uslan farm near Clarksburg. The 2025 season saw five active nest boxes fledge fourteen kestrels. On the Uslan farm three boxes were occupied and fledged nine young.
Nests in the project are checked frequently from March through August to document the timing of egg laying, growth and fledging of young, presence of predators, and other information relevant to nesting. These data are added to an international program administered by Cornell University called Nestwatch and used to help understand the status of breeding bird populations, how they may be changing, and the reasons for change.
Nest box placement strategies and management are now coordinated among Yolo, Solano, and Napa Counties, thanks to Dr. Breanna Martinico, Solano County Advisor with the UC Cooperative Extension. Through Dr. Martinico’s efforts, researchers from UC Davis are using occupied nest boxes to learn more about kestrel post-fledging dispersal, breeding home range size and habitat use, and other life history and demographic information. The Yolo, Napa, and Solano County teams will begin monitoring for the 2026 season in March and research collaborations with the University are expected to continue.
To learn more about this fine falcon, visit National Audubon’s American Kestrel page. For more information about kestrels or the nest box project, contact John McNerney or Kevin Hunting. Dr. Martinico seeks donations to support the program. Visit her site at bmartinico.wixsite.com/ucce-kestrel-program.
–Michael Perrone and Kevin Hunting