American Kestrel (Falco sparverius)

The American Kestrel is North America’s smallest and most colorful falcon, and many adore kestrels for their lovely plumage and big personality. In the 1800s and early 1900s, many referred to American Kestrels as “sparrowhawks,” however that common name typically refers to Accipiter hawks. Thus, scientists shifted to using the common name “American Kestrel”, because it is a more accurate descriptor and aligns with other small kestrels around the world. The American Kestrel’s Latin name, Falco sparverius, means “Falcon of sparrows” - a reference to this falcon’s habit of occasionally taking small passerines as prey.

Physical Description

American Kestrels are approximately the size of a jay, with the slender, pointed wings and long tail typical for falcons. They are approximately 9 inches long from beak to tail tip, and their wingspan is about 22 inches. Adults weigh an average of 4.1oz, or 117g. As with most other birds of prey, the female kestrel is larger and heavier than the male. However, with their small size and generally slender bodies, the size dimorphism is not readily apparent unless the pair is viewed right next to each other. Only then do the females appear more robust.

Their flight is buoyant and quick, and kestrels are known for hovering over fields as a hunting technique. Another great behavioral marker is that these birds tend to bob their tail while perching. They will often perch prominently on fence posts and power lines above their favored habitat, making it fairly easy to determine when American Kestrels are around. Confusing kestrels with doves or pigeons can happen, as both have the pointed wings, but the different tail shapes, the bright colors, and the very slender body of the kestrel can assist differentiation in the field. Doves and pigeons also do not bob their tail repeatedly while perching – a very useful behavioral distinction. Another similar species is the Merlin, which is also a small, slender falcon. However, Merlins typically fly fast and low to the ground, which is less common in kestrels. Merlins also sport much darker and less varied plumage overall.

male female american kestrel
American Kestrel males (left) have slate-blue wings and bright rufous-orange on their backs, tails, and heads. Females (right) are rufous-brown with black barring. Photos by Rob Palmer.

In comparison to other falcons in the United States, American Kestrels exhibit stark sexual dimorphism in coloration, with the male sporting bright, colorful plumage. Males have slate-blue over the top of their wings, with stark black primaries and secondaries spotted with white. The males’ backs are a rufous orange with black barring, and their tail is the same color with one large black band towards the end of the tail, lined with a few strips of white at the edges. The males also have a cleaner, whiter look to their sides, breast, and flanks – their belly is mostly white with black spots, and often a tinge of orange on their breast.

The females are more camouflaged in their appearance, sporting plumage with less stark contrast than the male. Female kestrels are a rufous-brown color overall and heavily-barred with dark brown across their back and tail. The females’ breast and flanks are streaked with brown over a cream base, and appear to be reddish and brownish throughout when viewed from a distance.

Both sexes have two stark black malar stripes on their cheeks, and a blue crown tinged with rufous at the very top. American Kestrels also have two spots on the back of their heads, acting as “false eyes” which may fool potential predators into thinking the kestrel will never be caught unwary from behind.

Subspecies of American Kestrels have some regional variation in their plumage, which is most apparent in males. For instance, male kestrels of the subspecies Falco s. sparverius exhibit light morphs and dark morphs, with the former almost completely lacking the typical black barring and spots. The South American Falco s. cinnamominus display the heaviest spotting and barring in both males and females, and are also the largest subspecies. Although subtle differences like these exist between all 17 American Kestrel subspecies, their unique color pattern still makes them readily identifiable across their entire range.

In South America, potentially confusing species include the Bat Hawk or Pearl Kite, if viewed very briefly in the wild, due to similar size or behavior, but the color of the American Kestrels’ plumage, and the falcon shape, is very different from either of those.

Range

American Kestrels are a generally widespread and adaptable species, found from Alaska all the way down to the southern tip of Argentina. In general, American Kestrels in colder climes tend to migrate to warmer regions for the winter months, while kestrels in sub-tropical and tropical regions are non-migratory. In areas where migrations happen, kestrels are spotted in the thousands during peak migration times at hawk migration watches stationed along major flyways.

Habitat Requirements

American Kestrels are an adaptable species in terms of climate, temperatures, and elevation. These little falcons are generally located anywhere in the Western Hemisphere that is not covered in dense forest or in the Arctic Circle. American Kestrels are a species of open country, generally preferring grasslands and shrub lands over anything with tree cover. Ideal kestrel habitat is composed of ample open space with snags, fence posts, lone bushes or trees, or power wires acting as isolated perches. Kestrels prefer to be able to see their entire territory easily from any one perch, and do not typically appear in areas with dense foliage.

Thus American Kestrels can be found in any of the following: deserts, plains, wooded savannah, marshes, farmland, tree lines and foothills of mountains, clear-cut areas, and even suburban and urban environments.

While wintering, females are seen in more open habitat than males. Some hypothesize this is simply because the females generally arrive at wintering grounds before males do, and thus the females claim the more preferred habitat.

american kestrel varied habitat types
American Kestrels nest in open habitat including pastures, plains, meadows, and agricultural fields and even suburban and urban environments. Photos by Sarah Schulwitz (left and middle) and Peter Green (right).

Food

As one might expect from a bird with a wide range like the American Kestrel, this species is varied and adaptable when it comes to diet. The vast majority of prey taken by American Kestrels is medium or large insects. Most kestrels also frequently prey on small mammals, such as voles or mice, and small lizards and snakes. Kestrels are also known to occasionally hunt bats, though this is less common than the aforementioned prey items. In arid and subtropical regions, small reptiles can make up the majority of a kestrel’s diet. Kestrels use isolated perches to sit and wait for prey, and they also actively search while flying, kiting, or hovering over fields. Captured prey is then eaten by the kestrel while perching.

american kestrel prey variety
American Kestrels have a varied diet includeing mostly insects and small rodents, but they'll even take small birds and reptiles. Photos by Peter Green (first and third), Jim Shane, and Don McCartney.

Life Cycle

Breeding

American Kestrels differ from many other North American falcons in that they prefer to nest in cavities, instead of cliff ledges. Kestrels do not construct their own cavities, however, and thus they are secondary cavity nesters. Kestrels choose a variety of cavity types, including old woodpecker holes, squirrel nests, crevices in barns and building roofs, man-made nest boxes, or other similar structures. American Kestrels do occasionally use old, sheltered bird nests, however this behavior is rare compared to cavity nesting. The male kestrel claims a nesting territory and identifies potential nest cavities. Males will escort potential mates to cavities within their territories and the female will choose the nest site. Females appear to select males based on their plumage, flight displays, and how ideal their claimed nesting territory and potential nest cavities appear to be. Copulation between pairs is frequent and can occur from the time that both birds are at the nest site until the first egg is laid. Not all copulations are fertile, but they affirm the social bond between the male and female for the duration of the nesting season.

kestrel nest types
American Kestrels are secondary cavity nesters. They do not build their own nest. Instead, they rely upon the old nest sites excavated by another species (woodpeckers). They will also readily use human-made nest boxes and even spaces provided by eaves and vents on houses or buildings. Photos by (left to right) Rob Palmer, Sarah Schulwitz, Ted Adams, and Peter Green. See instructions for making a nest box.

Females will lay anywhere from 1 to 7 eggs, with 4-5 being the average. One egg is typically laid every other day, and incubation begins in full after the clutch is complete. The male or female may incubate the eggs briefly during the laying period, but incubation becomes a full-time job after the female is done laying eggs entirely. The female typically performs the majority of the incubation, with the male hunting and bringing her food. The male will assist in incubation, however, and the female can hunt for herself on occasion as well. Incubation of the eggs typically takes 27-31 days.

American Kestrel nestlings are born altricial, meaning blind and helpless. Though they are covered in a fine layer of white down, the down is not sufficient for thermoregulation, so the nestlings rely on the parents to keep warm. Much like with incubation, the female performs most of the brooding, and the male provides most of the food, but the male and female will sometimes swap jobs. The nestlings grow rapidly—their eyes opening a few days after hatching. Kestrel chicks reach their full adult body size in about 20 days of age.

Their feathers are grown in enough to make their first flights around 27-32 days of age. The act of first leaving the nest cavity is called “fledging,” and chicks that have fledged are referred to as “fledglings.” Fledging does not typically mean a graceful or competent flight occurred, however, and fledglings often end up on the ground after their first flights. Fledglings are capable of flying or climbing up to trees or bushes within a couple hours. During this period, the adult male and female will feed and protect the young birds as they make their first forays outside of the nesting cavity.

kestrel eggs nestlings
American Kestrels typically lay 4-5 eggs, which are incubated by both parents for about 30 days. Nestlings develop for another 30 days before they are ready to leave the nest, referred to as fledging. Photos by AKP Staff and Don McCartney (third) and Lou Ann Harris (fourth). See Nestling Aging Guide (must be signed in to access).

Non-breeding Season

Once kestrels have fledged, they'll remain in contact with their parents for the next few weeks before reaching independence. Groups of fledgling may join together in hunting flocks that may include young from several nests.

Populations of American Kestrels range from fully migratory to non-migratory. By late summer, some kestrel populations may be preparing to migrate to their wintering grounds. Scientists are still learning about where it is that different breeding populations migrate for winter and the routes they take to get there. On their wintering grounds, kestrels are also territorial.

Long-term and Range-wide Declines of Kestrel Populations

This charasmatic little falcon is in decline across North America and has been so since at least the 1960s. Scientists do not yet know why. Explore a map of North America to see how kestrels are faring in your region. Read what the American Kestrel Partnership is doing to understand these declines and how you can get involved.


Additional Information Sources

Download our Guide to American Kestrel Biology & Nest Box Monitoring.

Download Nestling Aging Guide: A Photographic Timeline of Hawk Mountain Sanctuary's American Kestrel Nestlings, By Klucsarits & Rusbuldt (must be signed in to access).

Click the Falco sparverius species account in Global Raptor Information Network to view additional information regarding:

  • Alternate Species names
  • Distribution
  • Subspecies
  • Taxonomy
  • Movements
  • Habitats preferred
  • Feeding Behavior
  • Conservation
  • Population estimates and trend

Bibliography Search: Search The Peregrine Fund’s immense research catalogue on birds of prey