Some Notes on Sparrowhawks

American Kestrel, Hull’s Gulch, Boise, Idaho

“Sparrowhawk” is the old name for American Kestrels, the pint-sized falcons that are probably the most common raptor in North America. Back in the day, pretty much all raptors were called “hawks.”¹ The name “Kestrel” derives from the Old French crecelle, meaning “rattle,” a reference to the sound of the bird’s cry.

While Kestrel populations are waxing and waning across North America, and there is some concern that exposure to organophosphates used in pesticides is having an adverse impact, they are still pretty common. American Kestrels are sexually dimorphic (technically, “dichromatic” as well) and the smallest North American raptor: males weigh about 111 grams; females about 120 grams.

While there are some thirteen species of kestrels worldwide, there is only the one species in North America, albeit with as many as seventeen subspecies. WC has seen Kestrels from Tierra del Fuego to the upper slopes of the Andes in Peru to Costa Rica to the Brooks Range in Alaska. It’s a pretty amazing range.

Kestrels are cavity nesters, like a lot of other species using abandoned woodpecker cavities. But Kestrels will also cheerfully use nesting boxes,² just one example of their adaptability to many of the impacts humans have had on their ranges and populations.

American Kestrel in a nest box, Camas Prairie, Idaho

Kestrels usually lay 4-5 eggs. About a third of the time the entire nest fails. Depending on geography and food supply, the nesting pair may try again. About two-thirds of the chicks will fledge. Life expectancy for a fledgling isn’t that great: a little over a one year. But if they make it through that difficult first year, Kestrel adults can expect to live as long as 11 years.

Kestrels hunt from perches, and part of their success is a result of their willingness to use manmade perches. Famously, they use wire cables and fences, but signs are perfectly acceptable, too. Kestrels have a beautiful hover flight, but that’s not their preferred or primary hunting technique.

American Kestrel hunting, Malheur National Wildlife Refuge, Oregon

Kestrels have a mutually beneficial relationship with farming. Kestrels hunt fields, especially the edges of fields. And they hunt mostly insects and rodents, critters that harm crops. It’s a win-win deal, something not all that common in the United States today. WC is unsure that farmers have gotten the message.³

American Kestrel, Boise, Idaho

WC thinks there is more ferocity packed in to this tiny, beautiful raptor than in any other North American bird. Because they are fairly common, we tend to take them for granted. That’s a mistake. This is an amazing bird.

 

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1. Northern Harriers were called “Marsh Hawks” as another example. Until pretty recently, the Northern Harrier specimen on display at the University of Alaska Museum of the North was still labeled a “Marsh Hawk.” ↩
2. Please don’t approach active Kestrel nest boxes. The photo below as taken from a distance of about 120 feet, with a 500mm lens and a 1.4X teleconverter, and even that far away you can see the bird was uncomfortable. Kestrels have been known to abandon their nests when harassed by humans. ↩
3. American Kestrels are the “white mice” of raptor studies. Their small size, reasonable adaptability to cages and short breeding cycle have made them a favorite for captive bird studies. WC has seriously mixed feelings about this. ↩