Black-chested buzzard eagle

Black-chested buzzard eagle
Scientific classification
Kingdom Information
Domain	Eukaryota
Kingdom	Animalia
Subkingdom	Bilateria
Branch	Deuterostomia
Phylum Information
Phylum	Chordata
Sub-phylum	Vertebrata
Infraphylum	Gnathostomata
Class Information
Superclass	Tetrapoda
Class	Aves
Sub-class	Neornithes
Infra-class	Neoaves
Order Information
Order	Accipitriformes
Sub-order	Accipitres
Family Information
Superfamily	Accipitroidea
Family	Accipitridae
Sub-family	Buteoninae
Genus Information
Genus	Geranoaetus
Species Information
Species	G. melanoleucus
Synonyms	Buteo melanoleucus Spizaetus melanoleucus
Population statistics
Population	Unknown
Conservation status	Least concern

The black-chested buzzard eagle (Geranoaetus melanoleucus) is a species of bird of prey of the family Accipitridae, and found throughout much of South America.

Description

Also known as the blue-headed eagle, or locally as the aguja (from Portuguese: águia; "eagle"), this species is considered more of a large buteonine hawk than an eagle, so its placement is undetermined. In the past, researchers have placed it within the genus Buteo (buzzard hawks) and Spitzaetus (hawk-eagles) before settling on Geranaetus, a name combined from two ancient Greek words (géranos, γέρανoς; aetós, ἆετός) which mean "crane eagle", and implying a similarity to cranes in coloration and vocalizations.

Assuming the black-chested buzzard eagle is a true buteonine hawk, it is among the largest and most powerfully built, with a body length of 23.6 to 29.9 inches, and a wingspan of 58.6 to 72.4 inches. Males are smaller than females, weighing about 59.9 ounces, with females weighing 81.1 ounces. The beak is relatively large and tall, but not eagle-like. The iris is brown, the waxy skin pale yellow as well as the unfeathered legs. The wings are long and broad, and very broad at the base, while the tail is short and wedge-shaped to rounded; it is largely hidden by the wings when the bird is resting, giving it a tailless appearance.

In adult birds the head and upper parts are bluish slate gray to blackish or dark russet brown. The upper breast is also colored and stands out clearly from the white underside. Fine white tips are present on many of these feathers. Cheek and throat feathers are lighter in color. Shoulder feathers and upper wing coverts are ash gray. The underside is whitish in color, and throughout the belly, the underwing coverts, and onto the secondary and primary flight feathers it is marked by fine dark banding.

Immature birds have a buzzard-like brownish appearance. They are blackish brown with cinnamon-colored whitish lines on the head and upper back, a light over-eye stripe and a beige to reddish light brown, darkly dashed or spotted throat and chest. The back, shoulder feathers and upper wing coverts are beige to reddish light brown lined. The underside is more or less dense dark banded up to monochrome dark brown.

Subspecies

• Geranoaetus melanoleucus australis; Andean mountain range: western Venezuela to Tierra del Fuego
• Geranoaetus melanoleucus melanoleucus; southeastern Brazil to Paraguay, Uruguay and northeastern Argentina

Habitat

The black-chested buzzard eagle inhabits light dry forests, savannahs with sparse tree coverage, transitional habitats between dry forest and pampas, pastures, and partly semi-desert-like bushland. It is particularly common in rocky mountainous landscapes with gorges and adjacent grasslands to find, but rarely rises to an alpine tundra ecosystem known as the Páramo. In Peru, it predominantly inhabits relatively dry areas in valleys and the western slope of the Andes, while it is usually rare on the rather humid, eastern-facing slopes. It usually ranges in elevation from sea level up to 11,000 feet, but begins in Colombia only from 4,800 feet, extends only up to 6,600 feet in Chile, and in Venezuela slightly over 13,500 feet. Occasionally the species has also been found at even higher elevations.

Diet

The black-chested buzzard eagle feeds on smaller mammals, birds and their nestlings, snakes and lizards, carrion, insect and other invertebrates. Mammals account for at least 80-95% of the prey. These include mainly rats, guinea pigs, skunks, as feral mammals introduced by man, such as hares and hares and rabbits. In a Chilean study, wild rabbits accounted for 44% and even 82% of the prey by weight. In northern Argentina, hares accounted for most of the food, while in Brazil, 81% of prey items were urban pigeons.

It hunts mainly by flight. The main activity falls on the morning and the afternoon; only in winter do the birds spend most of the day in flight. Often the species is seen hunting in pairs and exploits the thermals on north and west-facing ridges.

Breeding

The breeding season varies by location; in Venezuela it is between February and August, in Ecuador between September and April. In Peru, it breeds between May and October; in central Argentina and Chile, however, between September and January, and further south to Tiera del Fuego, between October and February. As southern Colombia has seen migratory birds between April and mid-July, the species on the equator may breed throughout the year.

The massive nest of branches measures nearly three feet in diameter and can grow over the years to over five feet. It is usually on projections or ledges in steep rocks, but sometimes in treetops, on power pylons, on saguaros or other large cactus, lower bushes or even on the ground. It is usually reused over a few years, but often also rebuilt elsewhere after some time, so that not infrequently several nests can be found within a radius of 160 yards around a long-standing breeding ground. Courtship and copulation usually take place over a period of two weeks.

The clutch consists of two, more rarely one or three eggs, which are incubated between 37 and 40 days. The chicks are white. In Brazil, a nestling time of 56 days, in central Chile of about 59 days was found. The chicks become independent only after about 10 months.

Threats

Not much is known about the total number of existing birds, as there is also uncertainty about its exact range. However, the species is generally common and lives in a very large area, so that a population of five-digit numbers is likely. The species is therefore regarded as "least concern" by the IUCN. Deforestation and the poisoning of carcasses for predator control, however, is cause for concern in localized areas where the birds are near human habitation.