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Grey-bellied Hawk - Accipiter poliogaster
#1
Grey-bellied Hawk - Accipiter poliogaster

[Image: autour.a.ventre.gris.jowf.0p.jpg]

Scientific classification 
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Genus: Accipiter
Species: A. poliogaster

Description: This medium-sized hawk measures 38–51 cm in body length, with females being considerably larger (by about 40%) than males. Other body measurements in the male have been recorded as 232–270mm flat wing length, 165–187mm tail length, 18–21mm bill length from culmen to cere and tarsus length of 50–55mm; Corresponding measurements in the female are 263–283mm flat wing length, 181–207mm tail length, 20–22mm bill length from culmen to cere and 53–60mm tarsus length.
The hawk's basic plumage is coloured black or dark grey above and contrasting white or grey on the throat and body underside below. As the common name suggests, the belly is pale grey. The head is black or very dark grey overall and extends halfway down the throat before suddenly becoming white, so as to give a “hooded” or “capped” appearance. In males, the crown is darker than the rest of the head, whereas the plumage on the back and head of the female is uniformly dark. White feathers on the nape are exposed and appear as white spots across the hindneck. The tail is black or grey with three wide light grey horizontal bands on top and a narrow white tip. The wings, legs and tail have been described as being relatively short for the body size, with a heavy bill and head.
The feet, legs, cere and orbital skin are yellow and the bill is black with a bluish grey base. The iris has been reported as yellow or red. Females are reported to have darker grey and the males light grey cheeks.
The plumage of juveniles has been said to resemble that of the Ornate Hawk-eagle and have even previously considered a separate species (A. pectoralis).
In the field, the grey-bellied hawk is similar in size and shape to the collared forest falcon and slaty-backed forest falcon and is therefore often confused with these two other species, both of which however differ markedly from the grey-bellied hawk in colouration. This hawk is most often seen soaring over forests and utters a cackling kek-kek-kek-kek-kek-kek that trails off the end. Average lifespan is estimated at 7.2 years.

[Image: 1800]

Distribution and habitat: This hawk has a wide but patchy distribution in tropical lowland evergreen forests of South America at elevations of 250-500m a.s.l. It occurs in northern and eastern Colombia, southern Venezuela, the two Guyanas, Suriname, eastern Ecuador, central and eastern Peru, Amazonian Brazil, northern Bolivia, eastern Paraguay and northeast Argentina. In Ecuador, its occurrence is patchy and has been observed only in pristine forest habitats. In French Guyana, it has been observed in the lower canopy of both primary and recently logged forests. The hawk is also said to occur accidentally in Costa Rica, with the first adult being observed here in 2014 after reports of only juveniles. It may be expanding its range into Costa Rica with the increase in human-disturbed land, which this hawk appears to tolerate as a nesting habitat. Alongside rainforest, this hawk is also found in patches of riparian forest, other dense woodland and sometimes in secondary forest. The total area of its occurrence is estimated at 7490000 km^2. Despite its large range, it appears to occur only locally and is generally rare.
Although it is generally considered to be resident throughout its range, partial or full migration has been reported, with austral migration from the south toward the equator in winter reportedly occurring March–June. In Ecuador, it has been sighted year-round and is therefore considered a permanent resident here (Global Raptor Information Network, 2012); and was once observed over 500m a.s.l at San Isidro.

[Image: Range_Map_Grey-Bellied_Hawk.jpg]

Feeding: Little is known about this hawk’s feeding biology; although given its medium size, it is assumed to take fairly large prey. The majority of prey may comprise small passerines and tinamous (Tinamus sp.). A young armadillo was also once identified as a prey item brought to the nest for young. This hawk is thought to be a still hunter. Instead of hunting by soaring, it probably perches in the forest canopy to wait for a passing prey.

[Image: IMG_5162.jpg]


Breeding: Breeding in this secretive hawk species has been observed and described only once in the field, which occurred in southern Brazil. It appears to nest in a manner typical for Neotropical Accipiter species, although grey-bellied hawk nestlings appear to stay longer in the nest (about 49 days) compared to nestlings of other hawk species. The single nest observed in Brazil constituted a platform built in the upper branches of a Parana pine. This tree may be the preferred nesting site because of dense accumulations of branches on top which may conceal the nest from potential predatory raptors. The clutch size in this nest comprised two eggs, with only a single nestling surviving and leaving the nest 49 days post-hatching.
Within a pair, the male hunts for food for the female to feed to the young; as for many other Accipiters. However, unlike in other Accipiter species, the female of the grey-bellied hawk does not bring food to the nestlings while they are growing.
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  • Claudiu Constantin Nicolaescu
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#2
Gray-bellied Hawk (Accipiter poliogaster) Observed Feeding on a Tinamou in Yasuni Biosphere Reserve, Ecuador.

On 20 May 2012, we observed a Gray-bellied Hawk while hiking through the primary forest on the Skutch trail at Shiripuno Amazon Lodge. The lodge is located along the Shiripuno River in the Yasuni Biosphere Reserve within the Orellana province of Ecuador (1u6.289S, 76u43.899W; 300 m asl). The sighting occurred at approximately 1100 H and lasted approximately 20 min. We first spotted the hawk flapping its dark wings as it landed on a branch about 15 m away from us, off the side of the trail, at an approximate height of 8 m. The hawk was feeding on an unknown species of medium-sized tinamou that it held in its talons. We observed the hawk feeding on the tinamou and a full crop was also evident. Based on the tinamou’s size relative to the Gray-bellied Hawk, grayish leg color, the habitat, and the geographical ranges of local species, we have limited the possible species of tinamou to either a Great Tinamou (Tinamus major) or a White-throated Tinamou (Tinamus guttatus). We recorded 1:37 min of video (which can be viewed at http://youtu.be/m_HiK7Ly7PA) and photographs, by digiscoping with a Canon Powershot camera through a 20X Swarovski spotting scope (Fig. 1), before it flew away with the tinamou in its talons.

[Image: JxH5ULa.png]
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