Kestrels: Dashing predators patrolling a landscape near you
By R. Gary Raham:
Nature compels me to draw her portraits and tell her stories. One of my favorite jobs over the past 27 years has been creating entrance signs for the City of Fort Collins Natural Areas. My latest sign, Kestrel Fields, inspired me to get to know America’s smallest falcon (Falco sparverius) a little better. I also discovered some ongoing research about kestrels along Colorado’s Front Range worth sharing. Kestrels, as it turns out, are one of those creatures who like some of the same habitat humans enjoy: open fields and parks dotted with trees. Sometimes, if no perches are available, kestrels will hover briefly before striking their prey. Kestrels may be just the addition your property needs to help control insects and small varmints while allowing you to witness a show of predatory prowess.
Many people refer to kestrels as sparrow hawks. Kestrels may eat sparrows, but they are truly falcons. The Eurasian sparrow hawk is a different bird, Accipiter nisus. Hawks and falcons, though both raptors (predatory birds with strong claws called talons), differ in several ways. Hawks tend to be larger (though not always), have wide wings for gliding, long tails, and broad chests. Hawks kill with their talons. Falcons are slender with pointed wings built for speed and agility. They sport white cheeks—adorned with flashy black swashes in the case of kestrels—and their beaks are hooked. Not to be indelicate, but kestrels and other falcons use those hooked beaks to twist and break the neck of their prey rather than pierce them with their talons.
During summer, kestrels dine on grasshoppers, cicadas, beetles, dragonflies, scorpions, spiders, and the occasional lizard for variety. Male kestrels, jauntily dressed in blue, black, and rust feathers, often offer food treats, like the fence lizard I’ve depicted in my illustration, to prospective mates. Females swoop in to critique the male’s selection. Males also scout out potential nesting sites—old flicker nesting holes, natural tree hollows, or human-provided nesting boxes—and show the real estate to their missus. The missus makes the final choice. Kestrels reside in Colorado year-round, although some individuals may be migrants. Kestrel pairs in sedentary populations tend to be monogamous and nest in either late April or early May, depending on the weather.
This is a good place to mention the ongoing kestrel research by CARRI—the Colorado Avian Research and Rehabilitation Institute (http://www.carriep.org/american-kestrel-research). Scott Rashid and his colleagues are searching for property owners living on prime kestrel real estate—open fields or meadows with posts or trees—to offer them access for placing nesting boxes. Over the past 5-6 years they have placed 156 boxes over a hundred-mile stretch from Parker to the Wyoming border. Rashid is well on his way to erecting 200 boxes within ten years, which will help increase kestrel populations. Some of the questions they are attempting to answer are:
What nesting sites and conditions produce the most chicks? Kestrels typically lay clutches of 3-5 mottled eggs, but the researchers have seen as many as 10 laid in a nesting box.
How does the elevation of the landscape impact the timing of egg laying? According to traditional wisdom, egg laying happens earlier at lower elevations.
How does the available prey impact nesting density?
How does the kind of food available at different sites impact nesting behavior and clutch size?
How does food for kestrels vary seasonally?
Although kestrels are our most common falcon, with a current estimated national population of 9.2 million, their numbers have declined by 1.39% from 1966 to 2017. (See the Cornell Lab site for more info: https://www.allaboutbirds.org/guide/American_Kestrel/lifehistory). Kestrels suffer losses from land clearing practices and the use of pesticides. Pesticides not only kill or impair kestrels directly as the top predators in their food chain, but also remove the insects that they need for food.
The CARRI nesting sites produced 127 young birds in 2020 and 84 in 2021—although they actually placed 35 more boxes in 2021. A heat wave at the wrong time destroyed some eggs. They are ready to expand their efforts in 2022.
When I first moved to Wellington, Colorado in the late 70s (When its population was about 1,200 people) kestrels were common along the back roads a few blocks away. Now, with a population around 10,000 (still not huge, I admit), kestrels have become scarcer. Fortunately, they still have places to flourish—like the kestrel fields on the west side of Fort Collins where my new sign will reside—but human growth inevitably impinges on their future success.
Now that I’m painting their pictures, I’m more aware of both their beauty and their plight—and so are you.
R. Gary Raham writes and illustrates both science fact and science fiction. Keep in touch with his work at www.rgaryraham.com