The rufous-thighed hawk (''Accipiter erythronemius'') is a small

hawk Hawks are birds of prey of the family Accipitridae. They are very widely distributed and are found on all continents, except Antarctica. The subfamily Accipitrinae includes goshawks, sparrowhawks, sharp-shinned hawks, and others. This ...

found from southern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

and southeastern

Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...

Paraguay Paraguay, officially the Republic of Paraguay, is a landlocked country in South America. It is bordered by Argentina to the Argentina–Paraguay border, south and southwest, Brazil to the Brazil–Paraguay border, east and northeast, and Boli ...

Uruguay Uruguay, officially the Oriental Republic of Uruguay, is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast, while bordering the Río de la Plata to the south and the A ...

and northern

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. It is usually considered a subspecies of the

sharp-shinned hawk The sharp-shinned hawk (''Accipiter striatus'') or northern sharp-shinned hawk, commonly known as a sharpie, is a small hawk, with males being the smallest hawks in the United States and Canada, but with the species averaging larger than some Neo ...

by most taxonomists, including the

American Ornithological Society The American Ornithological Society (AOS) is an ornithological organization based in the United States. The society was formed in October 2016 by the merger of the American Ornithologists' Union (AOU) and the Cooper Ornithological Society. Its ...

, but the

taxonomy image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...

is far from resolved, with some authorities considering the southern

taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

to represent three separate species: white-breasted hawk (''A. chionogaster''), plain-breasted hawk (''A. ventralis''), and rufous-thighed hawk (''A. erythronemius'').

Taxonomy

The breeding ranges of the rufous-thighed and sharp-shinned hawk is entirely

allopatric Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...

. This allopatry combined with differences in plumage (''see appearance'') and, apparently, certain measurements, has been the background for the split, but hard scientific data are presently lacking ( AOU).

Description

This is a small ''

Accipiter ''Accipiter'' () is a genus of birds of prey in the family Accipitridae. Some species are called sparrowhawks, but there are many sparrowhawks in other genera such as '' Tachyspiza''. These birds are slender with short, broad, rounded wings and ...

'' hawk, with males long, with a wingspan of and weight from . As common in ''Accipiter'' hawks, females are distinctly larger in size, averaging some 30% longer, and with a weight advantage of more than 50% being common. The female measures in length, has a wingspan of and weighs . The wings measure each, the tail is long and the tarsus is . Measurements given here are for the sharp-shinned hawk, but they are comparable for the remaining species.''Raptors of the World'' by Ferguson-Lees, Christie, Franklin, Mead, and Burton. Houghton Mifflin (2001), Adults have short broad wings and a medium-length tail banded in blackish and gray with the tip varying among individuals from slightly notched through square to slightly rounded (often narrowly tipped white). The

remiges Flight feathers (''Pennae volatus'') are the long, stiff, asymmetrically shaped, but symmetrically paired pennaceous feathers on the wings or tail of a bird; those on the wings are called remiges (), singular remex (), while those on the ta ...

(typically only visible in flight) are whitish barred blackish. The legs are long and very slender (hence the common name) and yellow. The hooked bill is black and the

cere The beak, bill, or Rostrum (anatomy), rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for pecking, wikt:grasp#Verb, grasping, and holding (in wikt:probe ...

is yellowish. The rufous-thighed hawk resembles the sharp-shinned hawk, but upperparts are darker, streaking to underparts rufous or dusky, cheeks are typically with a clear rufous patch (occasionally lacking almost entirely) and iris is yellow (''contra'' illustrations in some books). Juveniles resemble juveniles of sharp-shinneds, but streaking to the underparts are typically restricted to throat and central underparts, with flanks scaled or barred (often also the belly).

Distribution

The species is found in

, north-eastern

and south-eastern

. It is, as far as known, resident in some regions and migratory in others. The movements are generally poorly understood, but it only occurs seasonally at some localities in Argentina. The rufous-thighed hawk is found in tropical and subtropical regions; both in lowlands and highlands.

Diet

These birds surprise and capture most of their prey from cover or while flying quickly through dense vegetation. They are adept at navigating dense thickets, although this hunting method is often hazardous to the hawk. The great majority of this hawk's prey are small birds, especially various

songbird A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 5,00 ...

s such as sparrows, wood-warblers,

finch The true finches are small to medium-sized passerine birds in the family Fringillidae. Finches generally have stout conical bills adapted for eating seeds and nuts and often have colourful plumage. They occupy a great range of habitats where the ...

es,

wren Wrens are a family, Troglodytidae, of small brown passerine birds. The family includes 96 species and is divided into 19 genera. All species are restricted to the New World except for the Eurasian wren that is widely distributed in the Old Worl ...

nuthatch The nuthatches () constitute a genus, ''Sitta'', of small passerine birds belonging to the family Sittidae. Characterised by large heads, short tails, and powerful bills and feet, nuthatches advertise their territory using loud, simple songs. Mo ...

es, tits,

icterid Icterids () or New World blackbirds make up a family, the Icteridae (), of small to medium-sized, often colorful, New World passerine birds. The family contains 108 species and is divided into 30 genera. Most species have black as a predominant ...

s and

thrushes The thrushes are a passerine bird family, Turdidae, with a worldwide distribution. The family was once much larger before biologists reclassified the former subfamily Saxicolinae, which includes the chats and European robins, as Old World flycat ...

. Typically, males will target smaller birds, such as sparrows and wood-warblers, and females will pursue larger prey, such as

thrush Thrush may refer to: Birds * Thrush (bird), any of the birds in the family Turdidae ** List of thrush species * Antthrushes, the Formicariidae family of birds * Dohrn's warbler, or Dohrn's thrush-babbler, a species ''Sylvia dohrni'' in the famil ...

es and flickers, leading to a lack of conflict between the sexes for prey. They often pluck the feathers off their prey on a post or other perch. Rarely, rufous-thighed hawks will also eat rodents, lizards, frogs, snakes, and large insects.

Reproduction

Rufous-thighed hawks construct a stick nest. Clutches of 3 to 8 eggs have been recorded, but 4 to 5 eggs is the typical clutch size. The eggs measure and weigh about . The incubation period is thought to average at about 30 days. After hatching, the young are brooded for 16 to 23 days by the female, while the male defends the territory and catches prey. The young fledge at the age of about a month and rely on their parents for feeding and protection another four weeks. The breeding behavior of the rufous-thighed hawk is comparably poorly known, but based on the available knowledge they appear to differ little from that of sharp-shinned hawks.

Conservation

The rufous-thighed hawk is fairly common (but easily overlooked due to their secretive behavior) and presently considered safe.

References

* Dickinson, E. (2003). ''The Howard and Moore Complete Checklist of the Birds of the World.'' Christopher Helm. * Ferguson-Lees, J., D. Christie, P. Burton, K. Franklin & D. Mead (2001). ''Raptors of the World''. Christopher Helm. * Sick, H. (1993). ''Birds in Brazil: A Natural History''. Princeton University Press. {{Taxonbar, from=Q642474 rufous-thighed hawk Birds of Brazil Birds of Paraguay Birds of Uruguay Birds of Argentina rufous-thighed hawk