Birds of Leelanau: The American Kestrel,
The American Kestrel, our most common and smallest falcon, is found from the Arctic Circle to the southern reaches of Argentina and Chile.
Michigan breeding bird surveys found this species to be breeding in every county bestowing on it the distinction of raptor having the most even distribution in the state. Throughout Michigan and in Leelanau County it is a common summer resident, common migrant, but less than common, though not necessarily rare, winter resident.
Since the primary sources of food for this kestrel are small mammals, reptiles, and insects, the chances that this species will be encountered in Leelanau County in winter decreases as the presence and depth of snow increases. However, on farms where ample sources of feed are available to sustain sizable flocks of English Sparrows, this falcon, also known as a “sparrow hawk”, under such conditions, can likely sustain itself regardless of snow depth.
Breeding pairs split up in winter with individual birds defending territory. Females tend to lay claim to territory that is more open and less vegetated while males select areas of denser vegetation.
Male, female, and juvenile American Kestrels have prominent mustache marks on both cheeks. All have dark eyes, which is typical of falcons. Kestrel wings are slim and pointed and their tails are long and square-tipped. The primary feature which distinguishes the male American Kestrel from the female is wing coloration. Males have blue-gray wings whereas the female‘s wings are reddish brown with dark barring. Typical of raptors, female kestrels (10 in.) do tend to be larger than males (9 in.). However, the size difference is not pronounced and is much less conspicuous than the difference in plumage.
The literature notes that albinism occurs. Moreover, a kestrel specimen has been recorded in which the sexual parts of the bird were female but the plumage was male.
Breeding season starts in April in southern Michigan and in May in the north. Males perform courtship flights during which they fly in wide circles while bending their wingtips downward as they emit their mating call. Males indulge in promiscuous matings before monogamous bonds are formed. They seek out open or partly open habitats with scattered trees, in meadows, cultivated fields, and to a lesser extent, urban areas. In the north, where forests are extensive, kestrels find places to live in forest openings that afford access to dead trees for nesting sites. In more urban and agricultural areas kestrel pairs accept man-made nesting boxes when natural nesting cavities are not available. Such boxes are typically mounted on poles at a height of 10-15 feet.
Ordinarily, as far north as Leelanau, there is one brood. Three to five eggs are laid at intervals. Nesting material in the cavity is sparse. The male brings food to the incubating female. Reportedly, when the male nears the nest with food he calls the female. She flies to him to receive the food and then returns to the nest. The male continues to supply food until the fledglings become independent.
American kestrels are the only falcons that regularly hunt by hovering (flapping their wings in one place) or by kiting (gliding into the wind at a speed equal to the wind). Most raptors both catch and kill their prey with their talons. Falcons, including kestrels, catch prey with their feet but utilize a kind of “tooth’ on either side of the beak to snap the spinal chord of their prey. They also cache excess kill in clumps of grass.
The literature suggests that biggest threats to this species, besides hard winters, are the use of pesticides in agriculture and the tendency of humans to eliminate most large dead trees which would otherwise afford cavities of sufficient size to accommodate kestrel nesting needs.
~bob c.