By Beth DEImling
The American Kestrel (Falco sparverius) is North America’s smallest falcon. They are most often seen on utility wires along roadsides, and a drive along a northern Indiana country road is likely to chase a kestrel or two off a utility wire. Their favored habitat is open country with short vegetation and few trees. They may also be seen hovering in place over open fields. Northern Indiana’s pastures, hay fields, and some farm fields furnish good kestrel habitat. They will use trees, especially dead ones, if those trees are in open areas, or at the edge of woods. In fact, kestrels generally nest in tree cavities. Since they cannot excavate their own cavities, they rely on old woodpecker holes or natural tree hollows, as well as rock crevices, and nooks in buildings and other human-built structures. They also take readily to nest boxes.
A kestrel’s wings are narrow and blunt-tipped, and they fly in a series of fluttery flaps followed by an open-winged glide. When perched, kestrels often pump their tails as if they are trying to balance. Males and females are similar in coloration, but the male has slate-blue wings, while the female’s wings are the same reddish brown as the rest of the back. Both sexes have dark marks on their faces, sometimes called `mustaches’ and `sideburns.’
Kestrels primarily eat insects and other invertebrates when these are available, and otherwise (as in winter in Indiana) will eat small rodents, like voles, mice, and shrews, and even small birds. They generally catch prey on the ground, though they will capture some insects in flight. Unlike humans, birds can see ultraviolet light. This enables kestrels to make out the trails of urine that small rodents leave as they run along the ground. Like neon diner signs, these bright paths may highlight the way to a meal—as has been observed in the Eurasian Kestrel, a close relative.
Kestrels have a huge range, nesting from the Arctic to Central America, and the east coast to the west across the U.S. and southern Canada. In winter, kestrels vacate all of Alaska and Canada, the northern plains states and New England. It is possible to find them in the hundreds at coastal migration sites—such as Cape May, New Jersey, or Kiptopeke, Virginia—in September or early October. Their conservation status is currently of `Least Concern.’ However, recent counts and breeding bird survey data have indicated declines in some areas—such as in New England, parts of the Pacific Coast, and Florida, where the state lists it as a threatened species. Habitat loss may be a factor in their declines, especially through felling of the standing dead trees these birds depend on for their nest sites. The American Kestrel is also losing prey sources and nesting cavities to so-called “clean” farming practices, which remove hedgerows, trees, and brush. An additional threat is exposure to pesticides and other pollutants, which can reduce clutch sizes and hatching success. For kestrels in North America, a larger problem with pesticides is that they do their job, destroying the insects, spiders, and other prey on which the birds depend.
Similar species, which might be confused with kestrels at a distance, are Merlins, Sharp-shinned Hawks, and Mourning Doves. Merlins, however, are stockier, and dark brown. Merlins target larger prey than kestrels, particularly shorebirds and other small to medium-sized birds, which they often chase on the wing. Merlins have near-constant wingbeats, and fly by flapping their wings continuously. Sharp-shinned Hawks are accipiters, which means that they have broader wings, longer tails, and proportionally smaller heads. Sharp-shinned Hawks also hunt in more heavily wooded areas than kestrels. Mourning Doves occupy the same habitats as kestrels and often sit on telephone wires. In proportion to the rest of the body, they have much smaller heads than kestrels and their tails are slender and pointed. In flight, Mourning Doves tend to fly fast and in straight lines, with nearly continuous wingbeats