GCBO's July Bird of the Month
American Kestrel
by Mike Williams
The American Kestrel, (Falco sparverius), is common throughout North, Central and South America.  It is a resident over much of its US range. It is a summer visitor in the extreme North and a winter visitor in the extreme Southern US (most notably South Texas).  Originally called a Sparrowhawk, it was renamed the American Kestrel in 1993 to avoid confusion with the European Sparrowhawk (Accipter nisus). First described by Linnaeus in 1758, the American Kestrel is a member of the order Falconiformes (note sometimes this order is known as Accipitriformes) and the family Falconidae. There are some 17 subspecies of which 3 are found in the US. It should also be noted that it has at times been considered one and the same as the European Kestrel. The American Kestrel is the smallest falcon in North America, slightly smaller than Merlin.
Found in towns, parks, open fields, and all open country, it typically feeds on large insects in the Summer. In winter, its diet changes to small rodents, mammals and birds due to insect scarcity.  It has also been known to take snakes, squirrels and even birds as large as flickers.
The American Kestrel is a diurnal (day) hunter scanning for prey from a favorite perch for much of the day. Once sighted, kestrels will often hover over their prey before pouncing on it with both feet. Smaller prey is eaten immediately but larger prey is typically taken back to a perch.
American Kestrels are monogamous for the season once paired, but females are incredibly promiscuous, mating with many males until they find one they like.  Their nests are usually tree cavities where they lay 3-7 white/pink eggs and incubate them for 30 days. The females do most of the incubation, only leaving the males to this duty while they feed. Kestrels are solitary for the rest of the year. 
The American Kestrel overall population is stable at some 4 million individuals. However, some subspecies are under pressure, particularly those found in the southern and eastern US due to habitat and nest loss and persecution.

The American Kestrel is a small, dainty falcon with pointed wings, two facial stripes, and a rusty colored back with black stripes. The male has blue/gray wings and cap with a brown patch. Underparts are usually buff colored and streaked black. The female is much browner, lighter underneath and is noticeably larger. Note the head is always boldly patterned. They often ride thermals, gliding with the odd wingbeat, but when they see prey, they will hover as described above. 
The call is a shrill screaming “killi killi killi” and typically higher pitched than other raptors. 

Interesting Facts:
  • The collective noun for a group of kestrels is a hover, a soar, or a flight.
  • The nestlings usually defecate on the walls of the nest cavities, giving them a whitewashed appearance.
  • Nonbreeding territories are established by the females first and the males have to make the best of what’s left.
  • In falconry terms, the kestrel is very lowly and in medieval history was only owned by knaves. Today kestrels are considered beginner birds for inexperienced falconers.
  • The average lifespan is about 5 years with the oldest wild bird being 11-12 years old.
  • Kestrels can see in ultraviolet and often track small mammals such as voles from the urine trails they leave. They will also cache food in various locations to sustain them when prey is scarce.
  • The name kestrel is derived from the French “crecelle” or rattle due to its cry. Slang names include grasshopper hawk, killy hawk, windhover, house hawk or sparrowhawk.

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