«

»

Aug 27 2011

Print this Post

Bicolored Hawk (Accipiter bicolor)

Bicolored Hawk

[order] ACCIPITRIFORMES | [family] Accipitridae | [latin] Accipiter bicolor | [authority] Vieillot, 1817 | [UK] Bicolored Hawk | [FR] Epervier bicolore | [DE] Zweifarben-Sperber | [ES] Azor Bicolor | [NL] Roodbroeksperwer

Subspecies

Monotypic species

Genus

Members of the genus Accipiter are small and medium-sized hawks, often called Sparrow-hawks or Goshawks. The females are almost invariably much larger than the males – in some cases weighing twice as much – a level of size dimorphism only exceptionally reached in any other genus Falconiformes. Their wings are short and rounded; the tail usually quite long. They are well adapted for flying through dense bush. Bird-catching Sparrow-hawks generally have long and slender legs, with slender digits, the middle one being especially long. Goshawks are usually larger, with shorter, thicker tarsi and digits and a shorter middle digit. Some smaller species have goshawk-like feet and vice versa, making it difficult on a world-wide basis to subdivide the genus on this or any other broad basis. Although many accipiters feed upon birds moreso than do other hawks, some species take many mammals, especially squirrels; others take lizards, frogs, snakes, insects, even snails. In these species the legs and digits are sometimes slender, but short. Accipiters are rarely crested, but some have very attractive colour patterns. Black phases are present, especially in the tropical species. One in Australia has the only pure white phase. Accipiter is the largest genus in the family, having about fifty species. It is present worldwide, but is especially rich in Papua-New Guinea, where a small island like New Britain may have three to five endemic species or distinct sub-species.

Physical charateristics

Accipiter bicolor bicolor resides in the Yucatan, south over northern South America, through the Amazon area and, in the tropics and subtropics of the Andes, to eastern Bolivia. The adult has a black crown; its upper parts are deep grey; and its tail black with two or three pale bars that appear white from below. Its primaries are faintly barred with a dusky shade. The underside is highly variable, from pale whitish grey with white under-tail coverts and throat, to dark grey. The thighs are bright rufous. The eyes are orange; the bare skin of the orbit, cere and legs is yellow, and the bill is black. The young are black to deep brown above; the feathers usually having paler edges, and a narrow huff or off-white collar, although this is sometimes indistinct. The tail is black with a white tip and three or four white or grey bars. Below, as the adult, it is variable: white, creamy buff or, occasionally, deep rufous. The thighs are usually more deeply coloured, sometimes mottled with dusky. The eyes are straw coloured, the cere and lores are a paler yellow than those of the adult. The legs are yellow. Accipiter bicolor fidens is found in Southern Mexico and is similar to Accipiter bicolor bicolor, but larger. Accipiter bicolor pileatus is the variant in Brazil, south of Amazonia. The adult is like a pale Accipiter bicolor bicolor, but is even paler and has a pearl grey collar, and the under-wing coverts as well as the thighs are rufous. Immatures are more mottled with buff and white above than are bicolor, below the colour varies as in bicolor, but it is heavily streaked with broad, black tear-shaped markings.Accipiter bicolor guttifer. The tropical area of southern Bolivia, northern Argentina, and the Paraguayan Chaco is home to this group. The under parts are tawny to rufous, mixed with grey in the male and flecked with white in the female. The throat and upper breast are usually grey; above is a little darker. The young much as in pileatus Accipiter bicolor chiliensis is to be found in the forested Andes of Chile and Argentina south to Tierra del Fuego and Staten Island. It is darker above than Accipiter bicolor guttifer. Below it is grey or brownish grey, heavily flecked and barred with white. The throat is white, occasionally with a suggestion of the tawny of guttifer. The thighs are rufous as in the other races. The young of this race are very like those of Accipiter bicolor guttifer.

Listen to the sound of Bicolored Hawk

[audio:http://www.planetofbirds.com/MASTER/ACCIPITRIFORMES/Accipitridae/sounds/Bicolored Hawk.mp3]

Copyright remark: Most sounds derived from xeno-canto


wingspan min.: 58 cm wingspan max.: 83 cm
size min.: 34 cm size max.: 45 cm
incubation min.: 20 days incubation max.: 23 days
fledging min.: 30 days fledging max.: 35 days
broods: 1   eggs min.: 1  
      eggs max.: 3  

Range

Latin America : South Mexico to North Argentina

Habitat

In Chile it is said to prefer woods of oaks and araucarias, but it generally prefers mixed clearings, not unbroken forest.

Reproduction

In guatemala Bicolored Hawks are year-round residents and establish nesting territories during the breeding season, which coincides with the late dry season and beginning of the wet season. Nest building and courtship spanned 92 days. Bicolored Hawk nests average 22 m above the ground in living trees 75 cm in diameter. All nests are stick nests, averaging 51 X 44 cm exterior diameter, 26 cm exterior depth, and 3.6 cm interior depth. Clutch size is 1-3 eggs, after clutch loss a second brood is laid. Incubation lasts about 35 days, the young fledge after 30-36 days.

In Chile it builds in mid-October a well constructed nest of green and dry sticks and other material. It is sited high in a tree, not very far from the edge of a forest. Four eggs are laid in late October. They are greyish white, sparingly marked light brown. Incubation is by the female and takes about 20 days.

Feeding habits

The diet consists principally of birds, especially doves.

Video Bicolored Hawk

httpv://www.youtube.com/watch?v=JaiB1SGsMkY

copyright: D. Ascanio


Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
With such a large range the possibilities for confusion with other species are many. In Brazil its resemblance to the Rufous-thighed Kite (Harpagus diodon) in both adult and immature plumage is so close as to suggest mimicry. It must also be separated with care from the smaller Sharp-shinned Hawk (Accipiter striatus) and the larger Grey-bellied Goshawk (Accipiter poliogasier). Various small falcons of the Micrastur genus, to which there is considerable resemblance, have longer, coarser legs.
Little is recorded of their lifestyle, except in Chile, which is not typical of the range of the species. It is a true accipiter, bold and rapacious, feeding chiefly on birds which it takes in a stealthy manner from a perch or by flying through cover. In Chile it is said to prefer woods of oaks and araucarias, but it generally prefers mixed clearings, not unbroken forest. It is said at times to hunt in pairs.
Bicolored Hawk status Least Concern

Migration

Very little data available, thought to be sedentary.

Distribution map

Bicolored Hawk distribution range map

About the author

admin

Permanent link to this article: http://www.planetofbirds.com/accipitriformes-accipitridae-bicolored-hawk-accipiter-bicolor

Leave a Reply