“Kestrels in California have been on a long downward trend since 1950 at least,” says GGRO Director Allen Fish, citing several potential reasons for the decline, including predation by other raptors. Pesticides destroy important food sources for kestrels and also sometimes poison the birds themselves. Rodenticides and insecticides work their way up the food chain and cause secondary poisoning, as do heavy metals like selenium, mercury, and lead. Loss of nesting sites is another problem: kestrels are cavity nesters and rely on old woodpecker holes and tree hollows; they do not excavate their own cavities. Very old trees are becoming harder to find in managed forests, says Fish, and dying trees with potential nesting cavities are often treated as fire tinder and removed for safety or aesthetic reasons. The Kestrel Campaign, a Bay Area volunteer group funded by Save Mount Diablo, hopes to help local kestrel populations recover by educating the public about issues like rodenticides, and installing kestrel nesting boxes on public and private land near Mount Diablo. The group installed 24 boxes last year and Brian Richardson, the team’s leader, says there has been nesting activity in some of them. “Such citizen science operations, along with focused removal of poisons from our environments, together have a great chance of tipping the scales back in favor of this charismatic and useful falcon,” says Fish.

Photo Credit: Rick Lewis

The country’s tiniest falcon—the stunning American kestrel—is declining throughout the United States, and California seems especially hard hit: Kestrel numbers during the Golden Gate Raptor Observatory’s annual autumn migration counts declined from nearly 800 in 1997 to just 300 in 2017.

“Kestrels in California have been on a long downward trend since 1950 at least,” says GGRO Director Allen Fish, citing several potential reasons for the decline, including predation by other raptors. Pesticides destroy important food sources for kestrels and also sometimes poison the birds themselves. Rodenticides and insecticides work their way up the food chain and cause secondary poisoning, as do heavy metals like selenium, mercury, and lead. Loss of nesting sites is another problem: kestrels are cavity nesters and rely on old woodpecker holes and tree hollows; they do not excavate their own cavities. Very old trees are becoming harder to find in managed forests, says Fish, and dying trees with potential nesting cavities are often treated as fire tinder and removed for safety or aesthetic reasons. The Kestrel Campaign, a Bay Area volunteer group funded by Save Mount Diablo, hopes to help local kestrel populations recover by educating the public about issues like rodenticides, and installing kestrel nesting boxes on public and private land near Mount Diablo. The group installed 24 boxes last year and Brian Richardson, the team’s leader, says there has been nesting activity in some of them. “Such citizen science operations, along with focused removal of poisons from our environments, together have a great chance of tipping the scales back in favor of this charismatic and useful falcon,” says Fish.

About the author

Lisa Owens Viani is a freelance writer and editor specializing in environmental, science, land use, and design topics. She writes for several national magazines including Landscape Architecture Magazine, ICON and Architecture, and has written for Estuary for many years. She is the co-founder of the nonprofit Raptors Are The Solution, www.raptorsarethesolution.org, which educates people about the role of birds of prey in the ecosystem and how rodenticides in the food web are affecting them.

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