White tailed buzzard

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White tailed buzzard
Immaturer White-tailed Buzzard (Helle Morphe)

Immaturer White-tailed Buzzard (Helle Morphe )

Systematics
Class : Birds (aves)
Order : Birds of prey (Accipitriformes)
Family : Hawk species (Accipitridae)
Subfamily : Buzzard-like (buteoninae)
Genre : Blue Buzzards ( Geranoaetus )
Type : White tailed buzzard
Scientific name
Geranoaetus albicaudatus
( Vieillot , 1816)

The white-tailed buzzard ( Geranoaetus albicaudatus , syn .: Buteo albicaudatus ) is a large, characteristic gray and white drawn buzzard of the genus Geranoaetus within the family of the hawk-like (Accipitriformes). It is primarily a South American species , only the northernmost breeding areas reach Central America , Mexico and the southern United States . It has the greatest north-south distribution among the buzzard-like. The species appears in a light and - much more rarely - a dark morph . The sexes are colored the same, females are up to 17% larger than males.

G. albicaudatus predominantly inhabits dry or moderately moist habitats in the lowlands and low mountain ranges , such as grass steppes and prairies with individual trees , but also occurs in extensively cultivated landscape types and in the vicinity of large cities such as Rio de Janeiro . He is an opportunistic food generalist who feeds on large insects , small mammals , reptiles, and amphibians . The overwhelming majority of the white-tailed buzzards remain in the breeding area throughout the year, only partial populations undertake short-distance migrations. Young birds migrate on a large scale.

The white tailed buzzard was first described by Louis Pierre Vieillot as Buteo albicaudatus in 1816 . In 2015 three closely related species were separated from Buteo under the generic name Geranoaetus . As of the end of 2019, three subspecies are recognized.

Although the species is considered endangered in Texas, their entire population appears to be safe (IUCN LC = least concern). It is common in places and has been able to expand its breeding area, especially in southeastern Brazil.

With the exception of the northernmost occurrences in Texas, the species has so far only been insufficiently investigated.

Appearance

Adult white tailed buzzard
Intensely marked, adult white-tailed buzzard

The white-tailed buzzard is a very typically colored, large buzzard, with a gray upper side, almost white, reddish-brown to gray-banded underside, a short, white tail with a prominent black subterminal band , long legs for a bird of prey and long legs with gray, deep black fingers on the underside Wings. A characteristic of the seated bird is a rust-brown or cinnamon-colored coloring of the shoulder plumage. Females are often colored a little darker and more intensely drawn, but there is no clear dimorphism in color . Also in terms of size, males and females can only be distinguished from one another to a limited extent, since the body size of the largest males corresponds to that of the smallest females. The melanistic individuals to be observed mainly among representatives of the nominate form are uniformly dark brown except for the matt white, black-banded tail. Young birds are particularly well characterized by their gray tail, the lack of rust-red band and the dark-speckled breast side. G. albicaudatus is one of the few buzzards with clear wing projections (the wings of the hand protrude beyond the tail of the seated bird).

White-winged buzzards fly with slow, powerful, deeply drawn wing beats and glide in a pronounced V-position . They often shake and when the conditions are favorable they "hang" in the wind with their wings spread out. The species can often be seen on the ground.

The size of males is between 46 and 52 centimeters, and females between 48 and 60 centimeters. Males weigh a maximum of 950 grams, females up to 1100 grams.

Calling young bird

Bright Morphe ( G. a. Hypsopodius )

The basic color of the entire upper side, the cheeks and the upper wing is light gray to slate gray; Females tend to be slightly darker in color. The throat is pure white or lightly dashed; a small area above the beak is also white. All the middle wing covers on the upper side are cinnamon-colored or reddish-brown, which gives the seated bird a characteristic shoulder and sometimes coat color. The entire underside is white, especially in the chest area, often without any marks, while the belly and lower tail-coverts are usually finely gray, gray-black or reddish-brown sputtered . The under wing coverts are largely white and, to a very variable extent, finely dashed gray or reddish brown. All wings are gray, clearly darkly edged and lined lengthways several times in fine dark gray. The deeply fingered hand wings are much darker, almost black. The short, slightly rounded tail is white on the top and bottom. Near the end of the tail, which is finely edged with white, there is a deep black band about 2.5 centimeters wide on both sides. The legs are fluffy feathered up to the intertarsial joint; this area can be completely undrawn, but it can also be dense gray or reddish brown. The legs are orange-yellow in all ages. The hooked bill is light bluish gray at the base and darkens towards the tip, the iris is chestnut brown. The beak color and the color of the iris do not change with age.

Dark morph

Shaking, juvenile, dark-morphed white-tailed buzzard

Blacklings seem to be a bit more common only south of the Amazon region and east of the Andes . The extent of melanism varies and ranges from saturated dark brown (with mostly rust-red or cinnamon-brown shoulder coloration) to dark black-brown, with a lack of reddish-brown shoulder coloration.

Typically colored, dark morphic white-tailed buzzards are dark brown-black on the entire top and bottom. Whitish spots can only be seen above the base of the beak and in the throat area. The color of the under wing coverts corresponds to that of the upper side plumage, the wings are dark silver gray, clearly darkly edged and lined with several dark lines. The wings of the hand are almost black. The tail is light gray-white on the top and matt white on the underside. The black subterminal band is formed like in light morphous individuals, but contrasts less strongly; the unfledged body regions also resemble those of the light-colored birds.

Youth plumage

Fledglings of the light morph are speckled with dark brown all over the top and chest. The mottling is caused by the light brown edges of most cover and body feathers. The belly is drawn less intensely, the under tail-coverts are often cream-colored without drawing. The under wing-coverts are colored like the upper-side plumage, the wings are slate-colored and margined only imperceptibly darker. The wings of the hand are dark gray. The tail is silver on both sides; both the white border and the black subterminal tape are not yet formed or only hinted at; Likewise, the characteristic reddish-brown shoulder coloration is missing in light morphous young birds. However, it appears after the second moult, after which the young birds wear immature plumage , which has the most essential drawing elements of the adult plumage . On the upper side, however, the young bird is blackish brown and not gray. Dark morphic juveniles are similar in color distribution to light morphic juveniles, but are much darker on the underside.

Mauser

Chicks begin to moult their downy clothes around 10 days old and when they fly out they wear their first juvenile plumage, in which not all large feathers have reached their full length. In the same year or at the beginning of the next year, they molt all body feathers and gradually the large feathers. This moult can last almost the entire second year of life. With the beginning of breeding maturity in the third year of life they molt into the adult plumage, females largely during the breeding and nestling period; Males change the body plumage and many cover feathers during the breeding season, the wings and control feathers only afterwards, and always in such a way that only small gaps arise in the large plumage and the ability to fly is fully preserved. Thereafter, a complete moult takes place every year in the same pattern.

Vocal repertoire

Typical is a multi-part call sequence with high, nasal-squeezed sound characteristics that begin with a long drawn-out element, which is followed by further calls with similar characteristics at increasing speed and often falling pitch. This call seems - varied in many ways - to be used largely universally and can be heard throughout the year by both sexes, both while seated and in flight. Higher, high-pitched, and screeching elements indicate greater arousal. It is less common to hear monosyllabic, lined up call sequences with a different number of individual elements that are reminiscent of owl calls .

distribution

Breeding area

Distribution area of ​​the white-tailed buzzard

The white tailed buzzard has the most extensive north - south distribution of all American birds of prey with breeding occurrences from 29 ° N to 42 ° S. The northernmost breeding areas are on the Texas Gulf Coast and continue in Tamaulipas , Mexico . Deposits on the offshore Padre Island and on other coastal islands in the region are extinct. The breeding sites in Arizona and New Mexico have not been occupied since around 1900. In Mexico, the species breeds in various places along the Pacific and Gulf coasts, in greater density on cleared areas on the Yucatán peninsula , with the exception of Belize , where it is rarely or only rarely found. Distributed on larger and smaller islands, the breeding areas continue across Central America to South America. Two of the Bocas Islands and the Pacific Islands off the coast of Panama are also populated . In general, G. albicaudatus seems to be more common on the Pacific coast of Central America than on the Gulf coast. Somewhat more dense occurrences are likely to exist in the province of Guanacaste in Costa Rica. North of the Amazon basin are mainly the Llanos of Venezuela and the Guayana states , as well as the moderately humid north and northeast of Brazil . On some Leeward Islands ( Aruba , Curaçao , Bonaire ) there are also small breeding populations. The species does not breed in the Amazon basin itself. In Colombia , which is flatly populated in the northeast and very sparsely populated further south, the species reaches its greatest western extent. In the valley of the Río Cauca , breeding areas extend between the central and western cordillera . Small breeding populations also exist in the humid savannas of southeastern Peru . In Brazil, G. albicaudatus occurs both in the wetter areas on the Atlantic coast and in the Cerrado , the drier inland; in the Pantanal, the never-flooded fringes and dry islands are breeding areas. To the east and south-east of it it is a breeding bird of the Gran Chaco in northern Argentina , eastern Bolivia and Paraguay . The southernmost breeding areas of this species are in the pampas of Uruguay and north-central Argentina.

habitat

Habitat of the species in the Brazilian Caatinga
Breeding habitat in the Pantanal

The white-tailed buzzard shows a clear preference for dry, semi-arid habitats, but is relatively adaptable and also occurs in at least temporarily moist habitats, but occasionally also in marshland and in aquatic landscapes such as the Pantanal . He needs low or sections with no ground cover and avoids too dense tree population. Watercourses seem to be a positive element of a favorable breeding habitat. Above all, it is a type of lowland and hill country level up to about 1000 meters above sea level. However, it occurs sporadically and in low density up to 1800 meters in Colombia and up to 2400 meters in Bolivia.

In the best-studied Texas breeding area, it inhabits grasslands and bush savannahs with sparse to loosened tree cover, especially with Yucca sp., Mesquites and Celtis pallida . Thorn bush steppes with different xerophyte vegetation also offer the species suitable habitats here, but especially in Mexico. In Central America and northern South America, it breeds in the loosely tree-lined grasslands of the plains and low mountain ranges, called llanos. The extensive cattle husbandry that is practiced here and in large parts south of the Amazon basin is tolerated by the white tailed buzzard; However, he avoids intensively used agricultural land, even if it is temporarily fallow. In the extensive breeding area of ​​central and south-central South America, it colonizes the dry eastern flank of the Andes in Bolivia, the dry cerrado of central Brazil and areas in the Pantanal. In the southeast it breeds in the dry as well as in the wet savannas; it also occurs in the relatively moist, often loosened palm-lined transition zones to the Atlantic rainforest . Here it reaches the greatest density of settlements and penetrates in places in coastal alluvial lands and outskirts of large cities. The southernmost known breeding grounds are in the pampas of northern Patagonia , which vary in dryness .

Migration and space requirements

Detailed studies on these parameters are lacking. As far as is known so far, the species remains in the breeding area year round. Larger collections of migratory white-tailed buzzards observed in parts of South America could be related to food shortages or distant bushfires; Bushfires provide abundant food resources for this species and are often visited by large flocks of birds of prey. Even migrating young birds occasionally form groups. Nevertheless, regular migrations of individual populations cannot be ruled out.

In Texas, surveys have shown average population densities of 0.18-0.21 breeding pairs per km².

Food and subsistence

Donkey hares are one of the largest animals a white-tailed buzzard can beat

The white tailed buzzard is regarded as a food generalist due to the very large variety of prey animals. However , if the focus is on the number of prey animals ( grasshoppers ) or the ingested biomass ( rodents ), he can also be considered a nutrition specialist. The food composition depends on the geographical location of the breeding area, but also strongly on the season. It is particularly different where rainy seasons and dry seasons alternate; in the humid savannas of southeast Brazil, for example, the number of birds captured during the dry season is four times greater than during the rainy season.

In terms of numbers, insects are at the top of the prey list by a large margin. Field locusts , crickets and scarab beetles predominate. Mammals make up the majority of the biomass with up to 77%. In the north, the white-tailed buzzard captured mainly cotton rat , pack rat , pocket gophers and various types of small-eared shrew , in the southeast are vesper mouse , South American field mice , grave mice , bats and opossums the most important prey. Among the mammals, hares , cottontail rabbits , and possums are the largest and heaviest animals this species can strike. Birds are also an important source of energy, especially during dry seasons; their share in the biomass is about 10%. The white-tailed buzzard kills a wide variety of passerines , but also pigeons , waders , ducks , railings and some species of toothed quail . Depending on the season and breeding area, reptiles and frogs can represent an important food component. It preyed on different types of iguanas , glass snakes and smooth lizards , as well as different types of snakes , especially snakes , but occasionally also poisonous types such as rattlesnakes . White-tailed buzzards of the coastal marshes also often prey on crabs and large earthworms ( Megascolecidae ).

Adult white tailed buzzard on a hide

G. albicaudatus has mastered various hunting techniques. In addition to high-seat hunting , in which he observes the surroundings from an elevated seat guard and grasps the prey on the ground after a short glide flight, he also uses other variants of flight hunting. So he patrols in a slow, low search flight over his feeding ground, occasionally shakes or "hangs" in favorable conditions with outstretched wings in the wind; Even with these hunting techniques, prey animals are tracked down on the ground and also beaten there. If the prey is killed - mostly by a bite in the neck or a claw grip - it immediately covers it, even if there are no food competitors in the vicinity. He prey on birds and flying insects in flight, or surprises them on branches using beak or claws. Often he walks slowly on the ground, especially to track down reptiles.

White-tailed buzzards often travel considerable distances in order to reach bushfires, the edges of which they fly to capture fleeing animals or to pick up dead ones. Especially immature buzzards gather on such occasions in small groups and socialize with other birds of prey. Occasionally white-tailed buzzards have been observed on carrion; they often try to steal prey from other birds of prey, but they themselves also become victims of kleptoparasitism .

Breeding biology

White-tailed buzzards become sexually mature at two years of age and occasionally brood at this age (almost always with an older partner). The majority do not begin to breed until they are three years old. You have a seasonal bond. Nothing is known about re-pairings in the following year. The information on the breeding phenology is incomplete. Fresh broods were found in Texas from January to August, in Central America and Colombia also from January, between February and April in Suriname and (probably) between September and January in Argentina. Outside of these areas, no data are known, except that the breeding season is within the respective dry seasons. White-tailed buzzards usually breed once a year, but if the clutch has lost a replacement brood often takes place, often in a new nest.

Pair formation, nest building and nest

The courtship ritual includes the typical buzzard show flights in which the partners climb high with frequent calls and especially the male shows flight acrobatics. The male often flies with a branch in its claws , which it alternately maneuvers into its beak and then back into its claws. Typical of the kind is the grass-plucking (grass-pulling), in which the partners end up on the floor and ausrupft the male tussock and drops again. Especially after the sightseeing flights there are frequent copulations that last into the laying period. The courtship period lasts relatively long with up to a month.

Where there are no taller trees, the nest is often built very low in bushes or on raised ground, otherwise often in isolated trees at a height of over 12 meters. The nest is a massive, usually slightly elliptical, flat construction made of dead and fresh branches and twigs, as well as material from perennials and bushes. It is laid out with fresh leaves and grass on the inside and camouflaged with leaves on the outside. Both the interior and exterior cladding will be serviced and renewed well into the nestling period. Since nests are reused, they can grow into large structures.

Clutch and young rearing

The clutch consists of 2 (1 - 4) matt white, relatively large and heavy, mostly unsigned eggs (rarely some red or brown spots on the blunt end) with an average size of 58.9 × 46.5 millimeters and an average weight of 70 grams . The clutch is completed within 48 hours. The female, which breeds most of the time and which hardly hunts itself during the breeding and first nestling period, is only replaced by the male for a short time. Hatching begins after 29 days at the earliest, but can be delayed by a few days if the cold persists. When hatching, the young wear a dense gray-white downy dress , have their eyes half open and can sit and keep their heads upright. Fratricide appears to occur but is likely to be rare. The nestlings can cut up prey on their own in around 28 days; The female began to take part in the supply of food a little earlier, and the young remain alone for a long time. They leave the nest after 49 days at the earliest. At this point they are wearing their first youth dress, but not all large feathers have reached their final length; their flying skills are therefore limited. They stay close to the nest and are looked after by the adult birds for a long time. It is not uncommon for them to be tolerated in the territory of one of the parents until the next breeding season, until they are vigorously driven away and widely dismigrated. As far as is known, they do not return to the place of their birth. Immature white tailed buzzards occasionally form groups and roam undirected.

The few details on breeding success and escape rate only concern small samples of clutches in Texas. There 51% of the broods that had started brought at least one young to fly; the reproductive number was 1.13 young per breeding pair.

Systematics

Adult, G. a. albicaudatus

The white tailed buzzard was first described by Louis Pierre Vieillot in 1816 as Buteo albicaudatus (La Buse à Queue blanche). The type specimen comes loud HBW from the province of Rio de Janeiro. It was not until 2015 that the species was identified according to the recommendation of F. Raposo do Amaral et al. due to the great genetic distance to other species of the genus from Buteo and placed in the genus Geranoaetus defined by Johann Jakob Kaup in 1844 . The other two members of this genus G. melanoleucus ( aguja ) and G. polyosoma ( red-backed buzzard ) are also the closest relatives, the latter is considered a sister species . The generic name is made up of the Greek γερανος (geranos) = crane and αετος (aetos) = eagle and refers either to the crane-gray color or the long legs of the species, the specific epithet is a combination of the two Latin words albus (white) and caudatus (tailed).

Adult, G. a. colonus

As of the end of 2019, three well-differentiated subspecies are recognized:

  • Geranoaetus albicaudatus albicaudatus ( Vieillot , 1816): The nominate form is widespread in South America south of the Amazon basin; it is the largest subspecies with mostly dark throats. In flight, the head and neck often appear to be detached from the rest of the body like a hood. Dark morphous birds with rust-brown coat markings are comparatively common.
  • G. a. colonus ( Berlepsch , 1892): Eastern Colombia, Venezuela, Guayana states and Leeward Islands and (rarely) Trinidad . South to the northern border of the Amazon lowlands and east to the Atlantic. Smallest and lightest subspecies. Top light gray, bottom white; mostly white-throated. Dark morphic individuals are very rare.
  • G. a. hypsopodius ( Gurney , 1876): Andean valleys of Colombia northwards across Central America, Mexico to Southeast Texas. Intermediate in size and color to the preceding; mostly white-throated. Dark morphs are extremely rare.

Persistence and Threat

The White Tailed Buzzard is listed as an endangered species in Texas according to the Washington Convention on the Protection of Species , the IUCN assesses the population as non-threatened (LC = least concern) and describes the population trend as "increasing". According to Christie, the distribution area is almost 10 million km², and extrapolations quantify the total population with 2 million individuals. There are no supraregional records of population density and the number of individuals. In Texas, the population has stabilized after a DDT- related decline since the ban on the insecticide in 1981. In southeastern Brazil and other regions of South America, the species is benefiting from increasing deforestation, which is creating new, usable habitats. Wherever strychnine is used by sheep farmers to combat predators, however, there are significant population losses, and increasing leisure tourism can also lead to the abandonment of breeding grounds, as the white-tailed hawk is very sensitive to disturbances during the breeding season.

literature

  • CC Farquhar: White-tailed Hawk (Geranoaetus albicaudatus). In: The Birds of North America (AF Poole, ed.). Edition 2.0 2009; Cornell Lab of Ornithology, Ithaca, NY, USA; https://doi.org/10.2173/bna.30
  • RO Bierregaard Jr. and JS Marks: White-tailed Hawk (Geranoaetus albicaudatus) . In: J. del Hoyo, A. Elliott, J. Sargatal, DA Christie, and E. de Juana (eds.). Handbook of the Birds of the World Alive . Lynx Edicions, Barcelona 2019 (downloaded from https://www.hbw.com/node/53129 on December 3, 2019).
  • James Ferguson-Lees , David A. Christie : Raptors of the World . Houghton Mifflin, Boston 2001, ISBN 0-618-12762-3 , pp. 990; 668-670 .

Web links

Commons : White-tailed Buzzard ( Geranoaetus albicaudatus )  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b CC Farquhar: White-tailed Hawk (Geranoaetus albicaudatus). In: The Birds of North America (AF Poole, ed.). Edition 2.0 2009; Cornell Lab of Ornithology, Ithaca, NY, USA; Introduction
  2. ↑ a b c d e f g h i j k l m n o James Ferguson-Lees , David A. Christie : Raptors of the World . Houghton Mifflin, Boston 2001, ISBN 0-618-12762-3 , pp. 990; Pp. 668 - 670 .
  3. ↑ a b c d e f g h i j k l m n o p q RO Bierregaard Jr. and JS Marks: White-tailed Hawk (Geranoaetus albicaudatus) . In: J. del Hoyo, A. Elliott, J. Sargatal, DA Christie, and E. de Juana (eds.). Handbook of the Birds of the World Alive . Lynx Edicions, Barcelona 2019
  4. ^ The Auk: Fifty-sixth Supplement to the American Ornithologists' Union: Check-list of North American Birds
  5. ^ A b BirdLife International 2016. Geranoaetus albicaudatus . The IUCN Red List of Threatened Species 2016: e.T22695906A93533542. http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22695906A93533542.en . Downloaded December 3, 2019.
  6. ↑ a b c d CC Farquhar: White-tailed Hawk (Geranoaetus albicaudatus). In: The Birds of North America (AF Poole, ed.). Edition 2.0 2009; Cornell Lab of Ornithology, Ithaca, NY, USA; Appearance
  7. ↑ CC Farquhar: White-tailed Hawk (Geranoaetus albicaudatus). In: The Birds of North America (AF Poole, ed.). Edition 2.0 2009; Cornell Lab of Ornithology, Ithaca, NY, USA; Behavior
  8. ↑ Xenocanto voice example: multi-part call sequence with an elongated input element
  9. ↑ Xenocanto voice example: The same call in greater excitement
  10. ↑ Xenocanto voice example: Lined up monosyllabic call
  11. ↑ a b c CC Farquhar: White-tailed Hawk (Geranoaetus albicaudatus). In: The Birds of North America (AF Poole, ed.). Edition 2.0 2009; Cornell Lab of Ornithology, Ithaca, NY, USA; Distribution, Migration and Habitat
  12. ^ Robert S. Ridgely and John A. Gwynne: A Guide to the Birds of Panama with Costa Rica, Nicaragua and Honduras. Princeton University Press 1989; ISBN 0-691-08529-3 pp. 102-103
  13. ^ A b Gary Stiles and Alexander Skutch: A Guide to the Birds of Costa Rica. Comstock Publishing Associate, Ithaka (NY) 1989; ISBN 978-0-8014-9600-4 p. 107
  14. ^ Aves de Colombia
  15. ↑ Editor's note. Without reference or location, David Ascanio et al. (David Ascanio, Gustavo Rodriguez and Robin Restall: Birds of Venezuela . Christopher Helm, London 2017; ISBN 978-1-4081-0535-1 . P. 118) 2700 meters above sea level.
  16. ↑ Camilo Viana Oliveira, Fabio Olmos, Manoel dos Santos-Filho and Christine Steiner São Bernardo: Observation of diurnial soaring Raptors in northeastern Brazil depends on Weather Conditions and Time and Day. In: Journal of Raptor Research, Issue 52; Episode 1; Pages 56 - 65 Abstract engl.
  17. ^ A b Marco A. Monteiro ranzinolli and José Carlos Motta Jr .: Small Mammal Selection by the White-tailed Hawk in Southeastern Brazil. In: The Wilson Journal of Ornithology Vol. 118, Issue 1, 2006; P. 91 - 98 pdf engl.
  18. ↑ a b c d e C. C. Farquhar: White-tailed Hawk (Geranoaetus albicaudatus). In: The Birds of North America (AF Poole, ed.). Edition 2.0 2009; Cornell Lab of Ornithology, Ithaca, NY, USA; Diet
  19. ↑ a b c Marco A. Monteiro Granzinolli and José Carlos Motta Jr .: Feeding ecology of the White-tailed Hawk (Buteo albicaudatus) in south-eastern Brazil. In: Emu, year 107 2007; P. 214 - 222 pdf engl.
  20. ↑ a b c d C. C. Farquhar: White-tailed Hawk (Geranoaetus albicaudatus). In: The Birds of North America (AF Poole, ed.). Edition 2.0 2009; Cornell Lab of Ornithology, Ithaca, NY, USA; Breeding, Demography and Sexual Behavior
  21. ^ Nouveau dictionnaire d'histoire naturelle, appliquée aux arts, à l'agriculture, à l'économie rurale et domestique, à la médecine, etc. Paris, Chez Deterville, 1816-19. P. 477 BHL
  22. ↑ a b F. Raposo do Amaral, FH Sheldon, A. Gamauf † , E. Haring, M. Riesing, LF Silveira, and A. Wajntal: Patterns and processes of diversification in a widespread and ecologically diverse avian group, the buteonine hawks (Aves, Accipitridae) In: Molecular Phylogenetics and Evolution Vol. 53; 2009; Pp. 703-715
  23. ^ R. Terry Chesser, Richard C. Banks, Kevin J. Burns, Carla Cicero, Jon L. Dunn et al. Fifty-sixth Supplement to the American Ornithologists' Union: Check-list of North American Birds . In: The Auk, Volume 132 Volume 3; 2015; Pp. 584 - 593 pdf engl.