ANIMAL ESTATE client 3.01/8.10: KESTREL
FROM ANIMAL ESTATES 3.0: CAMBRIDGE
SCIENTIFIC NAME: Falco sparverius
ANIMAL PROFILE: The Kestrel is the smallest falcon in North America—about the size of an American Robin. Like all raptors, the American Kestrel is sexually dimorphic, although there is some overlap within the species. The female ranges in length from 23 to 28 centimeters (9-11 inches) with a wingspan of 53–61 centimeters (21–24 inches) and weighs an average of 120 grams (4.2 ounces). The length of the male varies between 20–25 centimeters (8–10 inches) with a wingspan ranging from 51–56 centimeters (20–22 inches) and weighing an average of 111 grams (3.9 ounces). These subtle differences are often difficult to discern in the field.
The coloration of the feathers, however, greatly varies between the sexes. Males have blue-grey secondary feathers on their wings, while the undersides are white with black barring. The back of the female American Kestrel is rufous with dark brown barring. The wings exhibit similar coloration and patterning to the back. The tail of the female is noticeably different from the male, being rufous in color with numerous narrow dark brown or black bars.
The kestrel has a sharp, hooked bill and large, talon-tipped feet that are ideal for hunting. The American Kestrel is the only North American falcon to habitually hover with rapid wing beats, keeping its head motionless while scanning the ground for prey. The kestrel commonly perches along fences and powerlines. They hunt large insects, bats, mice, birds and small reptiles. They rarely chase prey, such as flying insects or bats, through the air.
Courtship begins shortly after the male establishes a territory. Three to seven eggs are laid (usually 4 or 5) over a period of 2 or 3 days. Eggs are white, cream or pale pink with an average size of 35 x 29 mm. In early courtship, he may give the "dive display", a series of climbs and dives 33 to 66 feet (10 to 20 m) with 3-5 "klee" notes given near the peak of each climb. He may present the female with food during courtship feeding. He may entice her to the nest site by calling. He may "flutter-glide" toward her with quick and shallow wing beats while carrying food and she may also beg for food by flutter-gliding. The female initiates copulation by bowing with her tail in line with her body or slightly raised.
Pair bonding among kestrels is strong and usually permanent. A pair is established after the male takes over a particular territory. Thereafter, a female will begin to hunt and associate herself with the male. The major components that will strengthen the bond between the two kestrels include courtship feeding of the female by the male, aerial displays and the search for a nest site. During the nesting period, the male provides the family with food. Three to seven eggs are laid (usually 4 or 5) over a period of 2 or 3 days. Eggs are white, cream or pale pink with an average size of 35 x 29 mm. Later, both will hunt as the nestlings mature and eventually leave the nest some 30 to 31 days after they hatch.
This falcon species is not long-lived. The oldest banded wild bird was 11 years and seven months old while a captive lived 17 years.
THEIR SONG: The American Kestrel has three basic vocalizations - the "klee" or "killy", the "whine", and the "chitter." The "klee" or "killy" is usually delivered as a rapid series - "killy, killy, killy, killy" when the kestrel is upset or excited. It is used at the apex of the dive display, during fights with other kestrels, and after unsuccessful hunting attempts.
The "whine" may last as long as one to two minutes and may be single or treble. The more intense the situation, the more likely the "whine" will move toward the treble extreme. "Whines" are given during courtship feeding and copulation. The treble whine is heard from breeding females and fledged hungry young.
The "chitter" is the most frequent vocalization in male - female interactions. Its volume and duration depends upon the stress or excitement of the situation. It is associated with friendly approaches and bodily contact between the sexes during breeding season. Occasionally a "chitter" follows a "whine."
Calling occurs throughout the day. Nestlings at two weeks can produce all three vocalizations. Female kestrels tend to have slightly lower pitched and harsher voices than males.
RANGE: American kestrel falcons are very widespread, ranging throughout the Western Hemisphere. They are found from above the Arctic Circle in Alaska and northwestern Canada, south through Canada and the United States, into Mexico, parts of Central America, and most of South America.In fact, the American kestrel is the smallest and most common falcon in this area. Most of the birds breeding in Canada and the northern United States migrate south in the winter, although some males stay as year-round residents. It is a very rare vagrant to western Europe.
HABITAT: American kestrels occur in a variety of habitats from sea level or below up to about 3,700 m (12,000 ft.) in the Rockies.
They require open ground for hunting and are most often found in habitats such as mountain meadows, marshlands, grasslands, deserts, open pine forests, and any kind of mixed woods or grasslands, agricultural land, vacant sites, airfields, along the edge of highways, etc. American Kestrels usually defend a territory of approximately half a square mile
In addition to requiring open space for hunting, American Kestrels seem to need perches for hunting from (e.g., telephone wires), cavities for nesting (either natural or man-made), and a sufficient food supply.
COMMUNITY: The American kestrel is, for the most part, not a social bird. During the mating season, males and females pair up and have joint territories. Presumably, the pair or the male defends the territory. The function of the territory may not be so much to ensure mating as to maintain a pair bond during the nesting season when the male is needed to help rear offspring.
HOME CONSTRUCTION: Kestrels are highly adaptable, and can nest in snags, deserted woodpecker holes, and other natural tree cavities, as well as in cliffs, dirt banks, under the eaves of buildings, and in nest boxes. The male influences the female in her choice of a nest site. The nest is simple, consisting of a shallow scrape.
BUILDING MOTIVATION: Kestrels are cavity nesters in order to protect the eggs during the 28 – 32 day incubation period, as well as the two – three weeks before the hatchlings can feed themselves
THREATS: Kestrel populations have declined in some areas. Since they consume primarily insects in the summer, it is possible that the use of pesticides has had an effect on them in recent decades. An even greater problem may be a scarcity of nest sites. Being a secondary cavity nester, the kestrel requires an abandoned woodpecker hole or similar cavity. Luckily, this little falcon will readily utilize man-made nestboxes. After 30 days, chicks leave the nest. The family remains as a unit for some time. The survival rate of chicks is about 50% under natural conditions, but it is usually higher under better conditions (e.g., human-provided nesting boxes).
Although man is the biggest threat to kestrels (by reducing the kestrals food source and nesting grounds), they could fall prey to a larger hawk or falcon and have even been killed by ravens on occasion. The domestic cat also poses a threat to these small birds. Crows and ravens are destructive to the eggs when left unprotected in the nest.
INTERESTING FACTS:
• Both sexes take turns incubating their eggs, a very rare situation among North American birds of prey where the female usually incubates exclusively. Both sexes have brooding patches.
• Falcons, including kestrels, exhibit an uncommon sexual dimorphism in that the female is substantially larger than the male.
• Falconry became a serious sport in England in 1066. You could tell the rank of an Englishmen by the falcon he carried on his wrist. The Old World kestrel was carried by priests.
• The American Kestral is also known as the “Sparrow Hawk” because in the dire winter months, the Kestral has been know to eat House Sparrows.
MAKING AN AMERICAN KESTRAL NESTING BOX:
There are various ways to make a simple and effective nesting box.
The following websites are extremely helpful in Kestral Nesting Box Construction:
http://www.kestrelsacrossamerica.org
http://www.shawcreekbirdsupply.com/plans_kestrel.htm
http://www.dnr.state.md.us/wildlife/wakestrelboxplan.html
Luckily, building a kestrel nest box is fairly easy; the challenging part is putting your nest box up in just the right place and in the right way so kestrels will use the box. Below are listed important tips to increase the chance that kestrels will use your nest box.
PUTTING YOUR NEST BOX UP:
(Tips from Kestrels Across America)
Building a kestrel nest box is fairly easy; the challenging part is putting your nest box up in just the right place and in the right way so kestrels will use the box. Be sure to follow all of these important tips to increase the chance that kestrels will use your nest box.
1. You must put your nest box in the right habitat. Kestrels are open country birds. They don't nest in forests. Look for places where you often see kestrels hunting. Your nest box is designed to take the place of natural nesting cavities in large trees. If there are plenty of large trees with woodpecker holes already there, keep looking. Ideally, you want to find a place where kestrels are hunting, but not nesting: a place where there are no large trees for nesting, but there is still open country with mice and insects for hunting.
2. Kestrels will nest fairly close (1/4 mile) to people, houses, etc., but they will not nest in your backyard in town. For best results, make sure your nest box is at least 200 yards away from people or buildings.
3. Farms, ranches, orchards, croplands or other agricultural areas are often ideal places to put up a nest box. It's great if your family, or a friend owns the land, but if not, don't trespass! You must get permission from the landowner first. You might need to teach the landowners about kestrels. Be sure to explain how kestrels help control the populations of rodents and insects.
4. Be safe! Children should never put up a kestrel nest box alone. Make sure at least one adult is helping. Contact professional tree climbers, pole climbers, firemen, or utility workers and ask if they will help you put the box up. Use a ladder and make sure someone holds the bottom of the ladder. Don't work alone!
5. Your nest box should be at least 10 feet above the ground, preferably between 15-20 feet high. You could go higher, but it is not necessary and it will usually make it more difficult to put the nest box up.
6. Mount the nest box so it is either vertical, or tilted just slightly towards the ground. Don't mount it tilted up towards the sky. You want to keep the rain out!
7. The nest box entrance hole should face east or southeast towards the rising sun. Make sure the box receives afternoon shade; mount it on the east side of the pole or tree. In warm climates this is especially important.
8. There are lots of ways to mount, or attach, the box. If you are mounting onto something wooden, large screws are best but good solid 16p nails will work too. Be sure to pre-drill holes in the box backboard, so you don't split it. Use two nails on the top and one or two on the bottom. Make sure the box is secure and won't wiggle. Remember, if the box isn't solidly secure, predators like raccoons might knock it loose, causing it to fall to the ground. If you are mounting onto something metal, pre-drill two holes on the top and two holes on the bottom of the backboard. Use bailing wire to wrap 3 or 4 times through your box holes and around the metal pole. Make sure the bailing wire is tight, and no loose ends are sticking out that could harm an incoming kestrel.
Kestrel Information Reference Pages:
The Birdhouse Network from the Cornell Lab of Ornothology
Kestrals Across America
Wikipedia
Richard and Diane Van Vleck – Personal Pages & webcam
Texas Parks and Wildlife
Animal Diversity Web
Kestrel Nesting Box Reference Sites:
http://www.kestrelsacrossamerica.org
http://www.wap.atfreeweb.com/kestrel
http://www.shawcreekbirdsupply.com/kestrel_program.htm
http://www.shawcreekbirdsupply.com/plans_kestrel.htm
http://www.npwrc.usgs.gov/resource/birds/kestrel/estab.htm