Once called the Sparrow Hawk, the American Kestrel (AMKE) is the smallest and most widespread falcon in the U.S. Although it does capture and eat birds, they represent only about 5% of an AMKE’s diet of primarily insects and small rodents—hence, the decision to change its common name from Sparrow Hawk. In addition, falcons are not literally hawks; the term “hawk” generally refers to buteos (e.g., Red-tailed Hawk) or accipiters (e.g., Sharp-shinned Hawk). The scientific name—Falco sparverius—still reflects the earlier name, though, since “sparve” is used to refer to sparrows in some parts of England. And for the terminally curious, “kestrel” derives from the French word “crecelle,” which is that language’s term for this bird. “Crecelle” also means “a noisy bell,” thought to refer to its call.
With breeding documented in 47 of the 50 states, Colorado has about 2.2% of the breeding population of AMKEs, tied for 7th place with Arizona. A friend of mine who lives in a small town about 50 miles northwest of Denver had a pair of American Kestrels (AMKEs) nesting in a nest box on the side of their house. The family first heard nestlings during the Father’s Day weekend (6/20). Since the box wasn’t easily monitorable, the humans had to wait for the nestlings to make themselves visible. Here are 2 photos of the most courageous (and probably the oldest) nestling, checking out the world outside around 7/13.
On 7/15, the first nestling fledged. AMKEs hatch asynchronously, meaning that the first egg laid typically is the first to hatch. As a result, the nestlings also often fledge asynchronously, over 2 or 3 days rather than all within a short period of time. This photo is the first fledgling shortly after he took the plunge, clinging to a juniper tree near the house. You can see how short his wing tips and tail are—good clues for differentiating a fledgling from an adult (if the goofy, what-is-this-world-all-about behavior isn’t clue enough). No wonder they need some time for those crucial feathers to grow and those flight muscles to mature!
This nesting fledged 3 young, all males and dubbed Huey, Dewey, and Louie by the host family. From the bulge at his throat, it looks like the fellow in the middle has a full crop—meaning he had just eaten something and the digestive process was beginning in an expanded portion of his esophagus called the “crop.” Male and female AMKE fledglings can be differentiated in the same way that the adults are: blue wings, male; rufous wings, female. Referred to as “sexual dimorphism,” such plumage differences don’t appear in most avian species until after the first molt. Instead, most nestlings and fledglings resemble the female’s drabber, less distinctive coloration. Perhaps the less brilliant palette and patterns serve as camouflage, making the female less easily spotted on the nest by predators; if so, the same would like be true for the youngsters as well.