Amelia is a female American kestrel (Falco sparverius) that came to us in July 2018 after being brought in by a client who found her on the ground. It is suspected that she flew into a tree and was stunned. Upon further examination, we realized she was missing her right eye, which we believe is the result from a previous injury that caused her eye to recede back into her skull. While she is able to fly, her lack of right eye does not provide a suitable condition for her to be able to live in the wild. As such, she joined the WSU Raptor Club in October of 2018.
Facts about the American kestrel
Kestrels are found throughout North America and much of South America, living in grasslands, semi-open forests, and urban and suburban areas. While Kestrels are fairly adaptable, they prefer open habitat with short vegetation and sparse trees or high places for them to nest and perch. They can be found quite frequently perched on power lines, and you can identify them by their head and tail bobbing, which is a territorial gesture.
Since American kestrels occupy such a wide range, there are multiple variations in plumage, behavior, preferred diet, and size between locations. Currently up to 17 different subspecies of American kestrel are recognized throughout the Americas. In the wild, kestrels often only live three years but have been known to survive up to 11 years in rare cases.
Hunting & diet:
American kestrels are opportunistic and will commonly eat small rodents, birds, bats, or small reptiles. Kestrels are also known to eat grasshoppers and other large insects. They have been reported taking down even larger prey like squirrels or pigeons! Kestrels are often seen hovering in place over a field, searching for prey. Hovering requires a lot of energy, and kestrels, along with hummingbirds and kingfishers, are the only birds in the world that can sustain a hover for any extended period of time without the help of a headwind. They are able to use their wings and tail to balance in one place while scanning the ground with their excellent eyesight. Kestrels have several methods of hunting, but their preferred method is waiting on a high perch, such as a tree or powerline and swooping at prey. If there’s no perch Kestrels may hover over a field instead.
Eyesight: Kestrel vision is thought to be between eight and 12 times sharper than ours. To put that in perspective, if you were to attach a piece of paper with writing on it to a wall and walk as far from it as you can while still being able to read the words, a Kestrel would be able to go eight to 12 times farther away and still be able to read it! This is because their vision is much sharper. Kestrels can also see in the ultraviolet range and use this adaptation to track down prey by detecting reflective urine trails left behind.
Males vs. females: Kestrels are somewhat unique in that they are sexually dimorphic in color. The males have blue-grey down their wings, a spotted chest, and one thick black band across the end of their tail (called a sub-terminal band). Females are brown on their backs and wings, have vertical dashes on their chests, and many stripes across their tail. This makes sex determination very easy – with most other raptors, DNA testing is required.
Mating & nesting:
American kestrels are seasonally monogamous raptors, normally taking a different mate each breeding season.
Kestrels nest in cavities, either naturally made crevasses, cavities made by other species like woodpeckers, or human-made cavities like nest boxes. Four to five eggs are laid from May to August depending on what latitude the kestrel is at, and they are then incubated for about 30 days before hatching. In another 30 days the young kestrels will be ready to fly for the first time, and they’ll be mostly independent of their parents two weeks after fledging.
Kestrels, like all other falcons, have distinct physical features not found in other raptors. These include the falcon’s tooth, malar stripes, distinctly pointy wings, and nasal tubercles. The falcon’s tooth is a small projection in the upper beak, just behind the tip, that fits neatly into their prey’s vertebrae, making it easy to snap and quickly kill their prey. A corresponding notch in the lower beak complements the “tooth.” Long, pointy, and narrow wings enable them to fly at high speeds. Kestrels in a stoop dive (a near vertical dive) can reach speeds of up to 60 miles per hour (Peregrine falcons can nearly quadruple this, reaching speeds of over 200 mph). Nasal tubercles are small bones found in the nose that allow falcons to breathe easier during high speed diving. Since kestrels are diurnal (hunting during the day), the dark malar stripes on the face help reduce glare from the sun.
American kestrels are the smallest falcon in North America (and the second smallest in the world – the smallest is the African pygmy falcon (Polihierax semitorquatus). There are seven falcons found in North America and five that can be seen in Washington state. In order from largest to smallest, these are the gyrfalcon (Falco rusticolus), the peregrine falcon (Falco peregrinus), the prairie falcon (Falco mexicanus), the merlin (Falco columbarius), and the American kestrel.