Designed by Paul Smith 2006. This website is copyrighted by law.
Material contained herewith may not be used without the prior written permission of FAUNA Paraguay.
Photographs on this web-site were taken by Paul Smith, Hemme Batjes, Regis Nossent,
Alberto Esquivel, Arne Lesterhuis, José Luis Cartes, Rebecca Zarza and Hugo del Castillo and are used with their permission.
ACCIPITRIDAE - BIRDS OF PREY
Thirty-five species in twenty-three genera (see below), the global taxonomy of raptors is extremely complex. This is a large heterogeneous family, though its members are instantly recognisable. Both the world´s smallest (Gampsonyx) and the world´s largest (Harpyia) species occur in Paraguay, the latter 90 times heavier than the former (maximum weights of 100g versus 9kg). The bill is short, but powerful and viciously hooked. Lower mandible is notched to aid cutting. In some species the upper mandible is toothed. Base of the bill is covered by a fleshy cere of uncertain function, through which the nostrils open. The tarsi of bird hunters are long and thin, those of eagles short, strong and thick. Three forward-facing toes and one opposable hallux, each armed with sharply-curved talons, that of the hallux being the longest. Toe pads are roughened to provide extra grip. Wings typically are long, broad and rounded, often with emarginated primaries to reduce turbulence and give a low stalling speed. Members of this family have 10 primaries and 11-25 secondaries. Tail with 12-14 rectrices, generally longest in forest dwelling species and those with atypical wing-shapes to aid manoeuvrability. Birds of Prey have excellent sight and hearing, but a poor sense of smell. There are a high density of cones on the two foveae of the retina, one of which is directed laterally and the other forwards giving binocular vision. They also possess the largest pecten relative to size of any birds, permitting shape recognition. The eye is semi-tubular in shape and does not move in the socket, angle of vision is changed by moving the head. A supraorbital bony shield and a prominent nictating membrane protect the eye when dashing through vegetation. Mimicry or striking resemblance between unrelated species is notable in this family. Chicks are nidicolous and semi-altricial, passing through two downy stages, the second denser than the first, before feathers begin to grow. Juveniles and immatures are frequently very different from adults, both in plumage and body shape, and in some species a complex series of plumage changes may take five years before adult plumage is attained. There is one complete moult each year. In general the primaries are moulted from the innermost towards the outermost and secondaries from the outermost towards the innermost. Females are larger than males, conspicuously so in some species.
Complexities of taxonomy means that no two classifications of the Acciptridae ever seem to agree. Here we present the main characteristics of the individual genera.
Leptodon "Grey-headed Kite" . Forest kite. Lacks bony shield above the eye. Blunt bill with single tooth. Long rounded tail and long, rounded wings. Legs short and robust. Lores bristled. Immature polymorphic.
Chondrohierax "Hook-billed Kite" - Snail-eating forest kite. Long wings nipped in at the base. Long tail. Bill large, blunt, lacking a tooth and with violently hooked tip. Feet weak with slender claws. Bare lores. Lacks bony shield above the eye. Highly polymoprhic.
Elanoides "Swallow-tailed Kite" - Aerial, insect-eating kite with long, forked tail and long, pointed wings. Bill and feet small. Pied plumage, lores densely feathered. Lacks bony shield above the eye.
Gampsonyx "Pearl Kite" - Tiny, whitish, falcon-like kite. Wings pointed. Talons smooth and flattened below, not grooved.
Elanus "Black-shouldered Kites" - Small, whitish, open-country kite. Wings long and pointed. Talons smooth and flattened below, not grooved. Bill and feet small. Hovers when hunting.
Rostrhamus "Slender-billed Kites" - Snail eating wetland kite. Upper mandible greatly elongated for picking snails from their shells. Basal joint of middle toe fused to next joint beyond it. Broad wings, medium-length tail slightly forked. Claws long, slender and pointed, but only slightly curved. Middle claw with serrated inner edge. Lores bare
Harpagus "Rufous-thighed Kites" - Forest kite and possible mimic. Basal joint of middle toe fused to next joint beyond it. Wings short and rounded. Small, stout bill. Two tooth-like projections on upper mandible.
Ictinia "Plumbeous Kites" - Aerial, insect-eating kites. Mostly greyish plumage. Long, pointed wings and slightly forked tails. Basal joint of middle toe fused to next joint beyond it. Bill with inconspicuous tooth on upper mandible.Legs short, with short, strongly-curved claws.
Circus "Harriers" - Long narrow wings and tail. Hunt with characteristic "harrying" flight, low over ground with much tilting. Rounded facial disk and large ear openings giving enhanced hearing. Bill small. Legs long and slender. Females much larger than males. Nest on the ground.
Accipiter "Sparrowhawks" - Bird-eating forest hawks, hunting with rapid chases. Short, rounded wings and long tails improve agility. Long, thin tarsi. Toes slender, middle toe especially long. Females much larger than males.
Geranospiza "Crane Hawk" - Long, "double-jointed" scutellate tarsus. Short outer toe. Weak bill. Small head. Wings short, broad and rounded with broad secondaries. Long tail. Plumage soft and lax, particularly short on thighs.
Leucopternis "White Hawks" - Buteo-like forest hawks with white plumage. Wings short and rounded, tail moderate length.
Buteogallus "Black Hawks" - Short, broad, rounded wings and short tail. Legs thick and long. Black adult plumage.
Heterospizias "Savanna Hawk" - Medium-sized orange-coloured hawk of open-country. Wings long, moderately pointed. Tail medium. Legs long. Semi-terrestrial.
Parabuteo "Harris Hawk" - Medium-sized hawk with long wings and long, rounded tail. Slender, strongly-curved talons. Buteo-like but different proportions.
Busarellus "Black-collared Hawk" - Large "fishing buzzard" with long, broad wings and short, broad tail. Bill long and moderately hooked. Legs long, underside of toes roughly prickled for holding fish.
Harpyhaliaetus "Solitary Eagles" - Huge open-country eagle. Wings long and broad, tail short. Bill medium. Legs long and unfeathered. Lores with a few scattered bristles. Crepuscular in habits.
Rupornis "Roadside Hawk" - Sometimes included within Buteo. Differences in plumage, moult pattern and osteology also suggest that it warrants its own genus.
Percnohierax "White-rumped Hawk" - Humid forest hawk with mostly black plumage. Sometimes included within Buteo but DNA evidence suggests it warrants its own genus.
Buteo "Buzzards" - Broad-winged, broad-tailed hawks adapted for soaring. Bill, legs and talons average. Tarsus usually bare. Many species polymorphic.
Morphnus "Crested Eagle" - Large forest eagle with rounded wings and long, broad secondaries. Very long tail. Legs unfeathered. Long occipital crest undivided.
Harpia "Harpy Eagle" - Huge forest eagle, the worlds largest. Rounded wings and long, broad secondaries. Very long tail. Massive feet and powerful, thick tarsi. Female much larger than male. Long occipital crest divided in two.
Spizaetus "Hawk-eagles" - Large forest eagles. Slender with short, rounded wings pinched in at base and long, rounded tail. Legs feathered and talons long. Long, pointed crest.
REFERENCES
Brown L & Amadon D 1989 - Eagles, Hawks and Falcons of the World - Wellfleet Press.
Campbell B & Lack E 1985 - A Dictionary of Birds - T & AD Poyser.
Ferguson-Lees J & Christie DA 2001 - Raptors of the World - Houghton Mifflin.
Thiollay JM 1994 - Accipitridae Handbook of the Birds of the World Volume 2 - Lynx Ediciones.
