庫柏鷹

庫柏鷹
保护状况
无危 （IUCN 3.1）
科學分類
界： 動物界 Animalia 門： 脊索動物門 Chordata 綱： 鳥綱 Aves 目： 隼形目 Falconiformes 科： 鹰科 Accipitridae 亞科： 鷹亞科 Accipitridae 屬： 鷹屬 Accipiter 種： A. cooperii
二名法
Accipiter cooperii (Bonaparte, 1828)

庫柏鷹（Accipiter cooperii），外號雞鷹，是一種原生於北美洲的中型鷹，從加拿大南部到墨西哥北部均去找到牠們的身影。與一般的鳥類一樣，雄鳥的體型較雌鳥小；而在密西西比河以東的體型普遍較在河以西的為大。

分類

Cooper's Hawk was first described by French naturalist Charles Lucien Bonaparte in 1828. It is a member of the goshawk genus Accipiter. This bird was named after the naturalist William Cooper, one of the founders of the New York Lyceum of Natural History (later the New York Academy of Sciences) in New York. 其他常見的名稱有：雞鷹、Big Blue Darter、墨西哥鷹、Quail Hawk、Striker及Swift Hawk等。

Description

Comparison of a male Cooper's Hawk (left) with a female Sharp-shinned Hawk (right)

The average size of an adult male ranges from 220 to 410 g (7.7–14.5 oz) with a length between 35 and 46 cm (14–18 in). The adult male is significantly smaller than the average female, which are 330 to 680 g (11.7–24 oz) and 42 to 50 cm (17–20 in) long. Its wingspan ranges from 62 to 90 cm (25–36 in). Individuals living in the eastern regions tend to be larger and heavier than those in the western regions. All have short rounded wings and a very long tail with dark bands, round-ended at the tip. Adults have red eyes and have a black cap, with blue-gray upper parts and white underparts with fine, thin, reddish bars. Their tail is blue gray on top and pale underneath, barred with black bands. Immatures have yellow eyes and have a brown cap, with brown upper parts and pale underparts with thin black streaks mostly ending at the belly. Their tail is brown on top and pale underneath, barred with dark bands. The eyes of this hawk, as in most predatory birds, face forward, enabling good depth perception for hunting and catching prey while flying at top speeds. They have hooked bills that are well adapted for tearing flesh of prey. Immatures are somewhat larger than a Sharp-shinned Hawk and smaller than a Northern Goshawk, though small males nearly overlap with large female Sharp-shinned Hawks, and large female Cooper's Hawks nearly overlap with small male Goshawks. The Cooper's Hawk appears long-necked in flight and has been described by birdwatchers as looking like a "flying cross". The Cooper’s Hawk is seen mostly flying with quick, consecutive wing beats and a short glide, though they may also soar.

Distribution and habitat

Their breeding range extends from southern Canada to northern Mexico. They are generally distributed more to the south than the other North American Accipiters, the Sharp-shinned Hawk and the Northern Goshawk. Birds from most of the Canadian and northern-U.S.-range migrate in winter, and some Cooper's Hawks winter as far south as Panama). The Cooper’s Hawk occur in various types of mixed deciduous forests and open woodlands, including small woodlots, riparian woodlands in dry country, open and pinyon woodlands, and forested mountainous regions and also now nests in many cities. They were once thought to be adverse to cities and towns, but are now fairly common urban and suburban birds. The cities provide plenty Rock Pigeon and Mourning Dove for the Cooper’s Hawk to prey on.

Sharp-shinned Hawks (which closely resemble this small Cooper's Hawk) are also attracted to backyard feeders by smaller birds

Behavior

Feeding

Eating a finch in a backyard with feeders

These birds capture prey from cover or while flying quickly through dense vegetation, relying almost totally on surprise. One study showed that this is a quite dangerous hunting style. More than 300 Cooper’s Hawk skeletons were investigated and 23% revealed healed fractures in the bones of the chest. Cooper's Hawks prey almost exclusively on small to mid-sized birds. Typical prey species include American Robins, other thrushes, jays, woodpeckers, European Starlings, quail, icterids, cuckoos, pigeons and doves. Birds preyed on can range in size from wood-warblers to Ring-necked Pheasants. They may also prey upon the raptor American Kestrel and other smaller raptors, including their cousin the Sharp-shinned Hawk. They have been known to rob nests and may supplement their diet with small mammals such as chipmunks, hares, mice, squirrels, and bats. Even more rarely, they may predate on lizards, frogs, or snakes. It normally catches its prey with its feet and kills it by repeatedly squeezing it and holding it away from its body until it dies. They have also been seen drowning their prey, holding it underwater until it stops moving. The hawks, in addition, often pluck the feathers off their prey on a post or other perch. They have been increasingly seen hunting smaller songbirds in backyards with feeders. They will perch in trees overlooking the feeders, then swoop down and scatter the other birds in order to capture one in flight. These hawks can also pursue their prey on the ground by half running and half flying.

Courtship

The Cooper’s Hawks are monogamous and most mate for life. Pairs will breed once a year and raise one brood per breeding season. Courtship displays include stylized flights with the wings positioned in a deep arc. During their flight displays the male will begin by diving toward the female. A slow speed-chase follows involving the male flying around the female exposing his expanded under tail coverts to her. The male raises his wings high above the back and flies in a wide arc with slow, rhythmic flapping. Courting usually occurs on bright, sunny days, in midmorning. After pairing has occurred, the males make a bowing display before beginning to build the nest.

Breeding

Juvenile

Their breeding habitats are forested areas. The breeding pair builds a stick nest in large trees. Over a two week period the pair builds the nest. The nests are piles of sticks around 27 inches in diameter and 6- 17 inches high with a cup- shaped depression in the middle that is 8 inches across and 4 inches deep. Their nests are built in pines, oaks, Douglas- firs, beeches, spruces, and other tree species usually on flat ground rather than on a hillside. The nests typically are about 25–50 feet high off the ground, halfway up the tree, and out on a horizontal branch. The clutch size is usually 3 to 5 eggs. The cobalt-blue eggs average about 48 x 38 mm (1.9 x 1.5 in) and weigh about 43 g (1.5 oz). The female incubates the eggs between 30 to 36 days. The hatchlings are about 28 g (1 oz) and 9 cm (3.8 in) long and are completely covered in white down. They are brooded for about two weeks by the female, while her mate forages for food. The fledging stage is reached at 25 to 34 days of age, though the offspring will return to the nest to be fed until they become independent around 8 weeks. Eggs and nestlings are preyed on, rarely, by raccoons, crows as well as other competing Cooper's Hawks. Adults rarely fall prey to larger raptors, namely Red-tailed Hawks, Great Horned Owls, Peregrine Falcons, Golden Eagles, and Northern Goshawks.

Communication

Cooper’s Hawks communicate using vocalizations and displays. Vocal is probably preferred over display, because the denseness of their habitat could prevent displays from being seen from a distance. Males are usually submissive to females and will listen for reassuring call notes the females make when they are willing to be approached. The males have a higher pitched voice than females.

Lifespan

Cooper’s Hawks have been known to live as long as 12 years in the wild. However, the oldest known living hawk was 20 years and 4 months old.

Status and conservation

Juvenile

At one time, Cooper's Hawks were heavily hunted in persecution for preying on poultry and were called "chicken hawks". It is now known that predation by these hawks on domestic animals borders are negligible, and they are rarely hunted these days. Cooper's Hawks' breeding success was also reduced by the use of the pesticide DDT, but the ban of DDT ended that threat. Since then, the adaptable Cooper's Hawk has thrived. However, one threat facing Cooper’s Hawks today is the degradation and loss of habitat. Management activities like logging may make their former habitat unsuitable for breeding.

延伸閱讀

• Sibley, David. The Sibley Guide to Birds. Knopf. 2000: 112–113. ISBN 0-679-45122-6. 
• Accipiter cooperii. ITIS. [22 February 2009]. They are very dome.

外部連結

• Cooper's Hawk Species Account – Cornell Lab of Ornithology
• Cooper's Hawk – USGS Patuxent Bird Identification InfoCenter
• Cooper's Hawk Information and Photos – South Dakota Birds and Birding
• Cooper's Hawk Wing & Weight data