The kestrel: the smallest North American raptor and probably the most common

By BILL CHAISSON
Older American birdwatchers, which is to say folks in their 60s or older, will likely remember when the falcons on this side of the pond were called the sparrow hawk, pigeon hawk, and duck hawk. Falcons hunt by striking birds out of the sky by diving down on them from above, so ours got their names from the purported size of their prey. But there is a whole other class of hawk that also kills birds, the accipiters. As it happens there is an entire group of accipiters that are also called “the sparrow-hawks,” so the American Ornithological Union took action. They are in charge of regulated vernacular names so as to minimize confusion among birdwatchers.

The American kestrel (Falco sparverius) is closely related to and resembles the common kestrel (Falco tinnunculus) of Europe, Asia, and Africa. In fact, it is the female American kestrel that most resembles the Old World species; both of them have light brown backs flecked with black. The male American kestrel has a slate-blue back crown and wings. The pigeon hawk, now called the merlin, and the duck hawk, now called the peregrine falcon, both have slate-blue backs as well, while the kestrel’s is light brown like that of its European counterpart.

The pair of kestrels that lives in my neighborhood seems to arrived on their breeding grounds last week. That, at least, is when I started hearing their familiar “killy, killy, killy” call as they fluttered around the premises. I say “fluttered” because although falcons can fly extremely quickly and directly, the kestrel is prone to doing a lot of hovering and even flying erratically and acrobatically as if it were chasing flying insects. This fluttery display is part of the male’s defense of his territory. He repeatedly climbs and dives, uttering the distinct call, which essentially translates to “mine, mine, mine.”

While there old names suggests that they eat a lot of sparrows, kestrels are more fond of insects and other invertebrates, although they do also prey on small mammals and birds. They perch on an exposed branch that gives them a wide view of their territory and use their extraordinary vision to spot prey from there. From the perch the bird will sally out and then hover in one place before dropping straight down on its next meal.

Gerard Manley Hopkins’ poem “The Wind-hover” uses the hovering habit of the kestrel to evoke the image of the crucified Jesus. “High there, how he rung upon the rein of a wimpling wing.” Wimpling means rippling, a fair description of the bird holding itself in one place on high by beating its wings in essentially a figure-eight pattern. Other birds hover, including nearly all tyrant flycatchers, but there is something thrilling about the kestrel, perhaps because of the sharp saber shape of its wings and the rapidity with which it drops out of the hover to the ground.

According to the Squam Lake Natural Science Center, the kestrel has two methods for hunting. One is the above described hover and drop. They fold their wings to their body and drop talons first, using the acceleration of gravity to increase their effective weight as they strike their prey. The other method is the classic falcon approach, which is to strike a bird at high speed where it is perched and then pursue it through the air if the “stoop” isn’t successful. Kestrels have been clocked flying at 39 mph. Because of their small size, kestrels may also be prey for larger hawks and owls.

Perhaps because of their small size — the range in weight from equivalent to a blue jay to a mourning dove — kestrels are more likely to be creatures of your backyard than a merlin or a peregrine, both of which are associated with much wilder settings. The kestrel is a hole-nester and can even be induced to take up residence in a bird box. Furthermore, they will also oust other birds if their holes are big enough. This includes flickers or other large woodpeckers.

They usually lay four to five eggs, and although the young are helpless at birth, they grow rapidly. Unlike many raptor species, kestrels are ready to breed the year after they were born. And they often do; it has been observed that there are very few single kestrels.

John James Audubon depicted the “sparrow-hawk” on Plate 142 of his famous folio and dutifully showed the female clutching a dead sparrow in her talons. Audubon remarked upon its ubiquity: “Every one knows the Sparrow-Hawk, the very mention of its name never fails to bring to mind some anecdote connected with its habits, and, as it commits no depredations on poultry, few disturb it, so that the natural increase of the species experiences no check from man. During the winter months especially it may be seen in the Southern States about every old field, orchard, barn-yard, or kitchen-garden, but seldom indeed in the interior of the forest.”

That said, the species has been declining in numbers for many years, according to the North American Breeding Bird Survey of the U.S. Geological Survey. They have declined by 50 percent since 1966 and even more dramatically in New England and coastal California. Researchers attribute a lot of their decline to loss of habitat, namely the elimination of nesting sites. The “clean farm” practices of recent decades include removal of hedgerows and chopping down of dead trees. In addition to destroying nest sites, these practices reduce the amount of habitat available to kestrel prey. The amount of pesticides used in agriculture and even in lawn care are also reducing the number of invertebrates and are poisoning some that survive to be kestrel prey.

As Audubon noted indirectly, the bird withdraws from the northern portion of its range in the winter, including northern New England. The N.H. Fish and Game site notes that its numbers have been declining in the state and that it arrives in April and leaves sometime in September. The Squam Lake Natural Science Center calls it “locally common throughout New Hampshire.” If you don’t have a kestrel in your neighborhood, you can attract one by putting up a nesting box. There is a design specifically designed for them and the plans are available on line. One sources is the nestwatch.org site of the Cornell Laboratory of Ornithology where there is a page called “All About Birdhouses.”