Broad-winged Hawk
| Broad-winged Hawk | |
|---|---|
 | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Falconiformes |
| Family: | Accipitridae |
| Genus: | Buteo |
| Species: | Buteo platypterus |
| Binomial name | |
| Buteo platypterus (Vieillot, 1823) | |
The Broad-winged Hawk (Buteo platypterus) is a small hawk of the genus Buteo. During the summer some subspecies are distributed over eastern North America, as far west as British Columbia and Texas; they then migrate south to winter in the neotropics from Mexico down to southern Brazil.Other subspecies are all-year residents on Caribbean islands. As in most raptors, females are slightly larger than males. Broad-winged Hawks' wings are relatively short and broad with a tapered, somewhat pointed appearance. There are two types of colouration: a dark morph with fewer white areas and a light morph that is more pale overall. Although the Broad-winged Hawk's numbers are relatively stable, populations are declining in some parts of its breeding range because of forest fragmentation.
Description
The Broad-winged Hawk is a relatively small bird, with a body size from 34 to 44 centimetres (13 to 17 in) in length and weighing anywhere from 265 to 560 grams (9.3 to 20 oz).As in most raptors, females are slightly larger than males. Broad-winged Hawks have relatively short and broad wings, pointed at the end, which have a tapered appearance unique to the species. The Broad-winged Hawk can grow a wingspan of 81 to 100 centimetres (32 to 39 in).Adults' bodies are a dark brown with a white belly and chest containing horizontal barring. While their tail can be a dark grey-black with white lines along the middle, base and tip.The young hawks have a slightly different colouring with more white and longitudinal barring instead of horizontal barring. There are two types of colouration: a dark morph with fewer white areas and a light morph that is more pale overall.The light morph of this bird is most likely to be confused with the Red-shouldered Hawk, but they have a longer, more heavily barred tail and wings with a solid rufous color in the adult which are usually distinctive. Rare dark morphs are a darker brown on both upperparts and underparts. Dark-morph Short-tailed Hawks are similar but are whitish under the tail with a single subterminal band.
Taxonomy
This species, Buteo platypterus, is in the family Accipitridae, which is placed in the order Falconiformes (or Accipitriformes). Currently thespecies is split up into six subspecies; each is named for its distribution, as listed below:
- Buteo platypterus platypterus – Northern Broad-winged Hawk that occurs throughout much of continental eastern North America.
- Buteo platypterus brunnescens – Puerto Rican Broad-winged Hawk that occurs in Puerto Rico.
- Buteo platypterus cubanensis – Cuban Broad-winged Hawk that occurs in Cuba.
- Buteo platypterus insulicola – Antigua Broad-winged Hawk that occurs in Antigua.
- Buteo platypterus rivierei – Dominican Broad-winged Hawk that occurs in Dominica, Martinique and St. Lucia.
- Buteo platypterus antillarum – Antillean Broad-winged Hawk that occurs in the Lesser Antilles from Saint Vincent and Grenada to Tobago, excluding Antigua.
Habitat and distribution
Broad-winged Hawks have a wide range in North America and South America, from southern Canada to southern Brazil. Their breeding range is in the northern and eastern parts of North America and some, not all, migrate in the winter to Florida, southern Mexico and northern South America. There are five subspecies that are endemic to the Caribbean that do not migrate. Thus, Broad-winged Hawks are partial migrants. Those subspecies that do migrate will fly in flocks of more than forty up to hundreds of thousands at heights anywhere from 550 metres (1,800 ft) to approximately 1,300 metres (4,300 ft). They soar using thermals to carry them through their journey of 3,000–6,000 kilometres (1,900–3,700 mi). Fall migration lasts for 70 days as birds migrate about 100 kilometres (62 mi) per day from North America, through Central America to South America without crossing salt water. The enormous flocks of soaring Broad-winged Hawks are termed kettles and are characteristic of many hawk migration spectacles in North America, such as at Hawk Cliff in Ontario, Hawk Ridge in Minnesota, Hawk Mountain in Pennsylvania, and the River of Raptors in Veracruz.
Broad-winged Hawks stay in areas up to an elevation of about 2,000 metres (6,600 ft). They breed in deciduous forests good for nesting and forage primarily in wetlands and meadows. While some birds have acclimatized themselves to living near humans even those birds avoid human settlements and interactions. In the winter the migrating subspecies of the hawks seek out similar conditions to their overwinteringhome, so they settle in deciduous and mixed forests.
Although the Broad-winged Hawk's numbers are relatively stable, populations are declining in some parts of its breeding range because of forest fragmentation. Since there are no threats to its survival, it is assessed as Least Concern on the IUCN Red List.
Behaviour
Vocalization
These hawks use vocalizations for communication with their mates and offspring. Also in territorial displays towards intruders like the Red-tailed Hawks or other threatening animals. The call sounds like a very high pitched kee-ee, almost like a whistle. When confronted with a threat Broad-winged Hawks will emit an alarm call consisting of stuttered and squealing whistles.
Diet
Broad-winged Hawks are carnivores. The types of food they eat depends on the time of year. During the summer or nesting season the parents and ultimately their chicks will eat small mammals, such as chipmunks, shrews, and voles, frogs, lizards, and sometimes even other nesting birds. In the winter months Broad-winged Hawks have been observed feeding on insects, frogs, snakes, crabs, and some smallmammals. To catch their prey Broad-winged Hawks will watch from low branches hiding in the foliage until a target is spotted. From their roost they will do a short fast glide to capture the prey. They give special attention to preparing their food for consumption, skinning frogs and snakes and plucking prey birds' feathers. Most small mammals on the other hand will be eaten whole. They rarely drink water and are able to survive solely with the water present in their prey.
Reproduction
These birds will have only one mate during the breeding season, possibly because the male also helps a small amount with the upbringing of the chicks.They will breed anywhere between April and August starting when they are two years old; completely sexually developed.To attract and court females the males will do a flight display including cartwheels, birds meet in air hooking together by their talons and spiraling down together, dives, and other aerial acrobatics. They will also compete and fight with other males for the chance to mate with a female. If one of the males is successful the mating pair will have only one brood per season consisting of one to four eggs. Both the male and female will build the nest out of sticks and twigs in a deciduous tree before the eggs are to be laid. Once they are though the brown-spotted eggs are usually 49 by 39 millimetres (1.9 × 1.5 in) and weigh about 42 grams (1.5 oz). The female will then develop a brood patch and incubate the eggs for 28 days or longer before they hatch. The hatchlings will appear semi-altricial; incapable of any complex coordination but have open eyes and are covered in down feathers.Chicks will have rapid body growth until they are almost at adult body size at which time they are capable of walking, flying and eating without parental help. While in the nest the female gives most of theparental care, protecting and taking care of the chicks. It is not unusual to have the male provide some food for the female and offspring but his visits are short lived. Once a prey item is obtained for the nest the female will tear off pieces and will feed the chicks till they are able to rip meat off on their own. Often the chicks will fight for possession of the offered morsel, the younger ones usually losing and not getting enough. Broad-winged Hawks will protect their nests in a show of aggression (i.e. diving and chasing) towards any suspected threat but they generally will not make physical contact. Predators of eggs and nestlings includes raccoons, crows, porcupines and American Black Bears and adults have been know to fall to Great Horned Owls and Bald Eagles. It will take the hatchlings five to six weeks before they are able to leave the nest. Some young even after that time will remain in the area of the nest for several weeks more.
No comments:
Post a Comment