Black-and-white Hawk-eagle
Encyclopedia
The Black-and-white Hawk-Eagle (Spizaetus melanoleucus, formerly Spizastur melanoleucus) is a bird of prey
species
in the eagle
and hawk
family
(Accipitridae
). It is found throughout a large part of tropical America
, from southern Mexico
to northern Argentina
.
". It is some 20-24 in (50–60 cm) long overall and weighs about 30 oz (850 g). The head, neck and body are white; a small crest forms a black spot on top of the head, and the area around the eyes, particularly towards the bill, is also black. The wings are black, and the bird has a brownish tail barred black-dark grey and with white tip. The iris is orange, the feet pale to bright yellow with black talons. The bill is black with a yellow cere
.
The sexes are alike in color, but the female is larger. Immature birds have pale edges on the upperwing coverts and some brownish-grey feathers on the back.
The Black-and-white Hawk-Eagle is hard to confuse with any other bird in its range. The Black-faced Hawk
(Leucopternis melanops) is very similar in overall coloration, but it is much smaller and has a black tail with a single bold white bar in the middle. The Ornate Hawk-Eagle (Spizaetus ornatus), presumably a very close relative of S. melanoleucus, looks quite similar when young. However, the wings, back and tail are much lighter in young S. ornatus, and they do not have the black eye-ring.
to Veracruz
in southern Mexico
southwards throughout Central America
, with the exception of most of El Salvador
and the Pacific coast of Nicaragua
. In South America
, it occurs on the Pacific side of the Andes
south to Ecuador
. The bulk of its range extends along the Caribbean
coast from northern Colombia
and Venezuela
to the Guianas, and south through eastern Brazil
, Paraguay
and Uruguay
to NE Argentina
, and from there westwards again to Beni
and Santa Cruz
in NE Bolivia
. A Black-and-white Hawk-Eagle population is also found in the Loreto Region
of NE Peru
; it is not known in how far this is isolated from the rest of the bird's range. The species is absent from western Amazonia, and it is not common in the lands to the east (e.g. in Minas Gerais
).
Its natural habitat
s are lowland forest
s of any type, though very dense and humid as well as savanna
-like semiarid habitat are not preferred. Habitat fragmentation
is not very well tolerated; though the species prefers a diverse habitat of mixed forest and shrubland, it requires large stands of closed-canopy
forest to thrive. Its range does not extend very far into the uplands, but one individual was sighted at an altitude of about 4,000 ft (c.1,200 m) ASL
in the Buena Vista Nature Reserve in Colombia's Sierra Nevada de Santa Marta
.
The food of this carnivore
consists of mammal
s, toad
s, squamates and in particular a wide variety of birds. Among the latter, it is known to prefer tree-living species, such as oropendola
s, aracari
s, tanager
s and cotinga
s. But ground- and waterbirds like tinamou
s, chachalaca
s, cormorant
s and the highly threatened Brazilian Merganser
(Mergus octosetaceus) have also been recorded as its prey. The Black-and-white Hawk-Eagle has been known to attack small monkey
s, though it is not clear with which intent. For as it seems, it has not been recorded to actually kill and eat a monkey.
Its preferred hunting technique is to soar high until it has spotted suitable prey, and then dive down on it, usually right into the forest canopy, but it has also been observed to catch a White Woodpecker
(Melanerpes candidus) that had been mobbing
it in mid-air, after launching itself from its perch. It likes to hunt along ridges and forest edges where it can access the canopy-level from an oblique direction rather than just from directly above, and where ground-living prey is also more accessible.
It nests in the forest canopy, building a stick nest high up in exposed trees on ridges and similar locations, from where good hunting grounds can be watched. Detailed observations on its nesting habits are nearly non-existent however. In Panama
, birds started to construct a nest in September, during a dry spell in the rainy season. But the main nesting season may start before the onset of the rainy season as the nesting attempt was abandoned when heavy rains recommenced. The scant other data agrees with this, and at least in Central America the nesting season seems to run from March to June or so.
There is a general lack of information on the Black-and-white Hawk-Eagle's movements and population status. Each bird seems to require a hunting territory of about 3,500 acres (1,400 hectars) at least. While the variety of habitat types in which it is found suggests that it is not particularly susceptible to changes in land use, it is apparently still a rare and local species almost anywhere in its range. The IUCN until 2000 classified it as a Near Threatened
species due to the uncertainties surrounding its status, but as no evidence of a marked decline has been found and as the bird is found across a wide range, it was downlisted to a Species of Least Concern
.
genus Spizastur, but has recently been moved to Spizaetus
e.g. by the American Ornithologists' Union
, as it appears that the Ornate Hawk-Eagle (S. ornatus) is its sister taxon. This has created quite some taxonomic confusion, which has largely gone unnoticed however:
Originally, the name Spizaetus melanoleucus was given by Louis Jean Pierre Vieillot
to the Black-chested Buzzard-eagle
in 1819, while the Black-and-white Hawk-Eagle had been described in 1816 by the very same scientist as Buteo melanoleucus. The former species was placed in Geranoaetus – also a monotypic genus – in 1844, while the Black-and-white Hawk-Eagle had been moved out of Buteo and into Spizastur a few years earlier.
Thus, the identical specific epithets never came into direct conflict until recently. But the Black-chested Eagle-buzzard's placement in a monotypic genus was always disputed, and several authors treated it in Buteo. However, they overlooked that Buteo melanoleucus was the original name of the Black-and-white Hawk-Eagle and thus as a senior homonym could not be applied to the later-described species. The correct specific name for the Black-chested Eagle-buzzard when placed in Buteo, Buteo fuscescens, was reestablished in the mid-20th century for a short time more by accident than anything else; as most late-20th-century researchers argued for retaining Geranoaetus, this name was dismissed as erroneous and essentially forgotten.
As the Black-and-white Hawk-Eagle has not been placed in Buteo since long, Article 59.3 of the ICZN
Code applies. According to this, a junior homonym replaced before 1961 is not rendered permanently invalid (as junior homonyms usually are) if "the substitute name is not in use" – which has been the case after Amadon's 1963 revision. Hence, in this case the scientific name Buteo melanoleucus can apply to the Black-chested Eagle-buzzard, even though the Black-and-white Hawk-Eagle was described under exactly that name earlier, while the senior homonym melanoleucus still applies to the latter species when placed in Spizaetus according to the usual ICZN rules. Consequently, the proper name to use for each bird has through a number of coincidences become the senior synonym of the other species.
Bird of prey
Birds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as birds that primarily hunt vertebrates, including other birds. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh....
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in the eagle
Eagle
Eagles are members of the bird family Accipitridae, and belong to several genera which are not necessarily closely related to each other. Most of the more than 60 species occur in Eurasia and Africa. Outside this area, just two species can be found in the United States and Canada, nine more in...
and hawk
Hawk
The term hawk can be used in several ways:* In strict usage in Australia and Africa, to mean any of the species in the subfamily Accipitrinae, which comprises the genera Accipiter, Micronisus, Melierax, Urotriorchis and Megatriorchis. The large and widespread Accipiter genus includes goshawks,...
family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
(Accipitridae
Accipitridae
The Accipitridae, one of the two major families within the order Accipitriformes , are a family of small to large birds with strongly hooked bills and variable morphology based on diet. They feed on a range of prey items from insects to medium-sized mammals, with a number feeding on carrion and a...
). It is found throughout a large part of tropical America
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
, from southern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
to northern Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
Description
As its name suggest, this is a black and white eagle, resembling the small typical eagles sometimes separated in "HieraaetusHieraaetus
The genus Hieraaetus, sometimes known as hawk-eagles, denoted a group of smallish eagles usually placed in the Buteoninae subfamily of accipitrids....
". It is some 20-24 in (50–60 cm) long overall and weighs about 30 oz (850 g). The head, neck and body are white; a small crest forms a black spot on top of the head, and the area around the eyes, particularly towards the bill, is also black. The wings are black, and the bird has a brownish tail barred black-dark grey and with white tip. The iris is orange, the feet pale to bright yellow with black talons. The bill is black with a yellow cere
Cère
The Cère is a long river in south-western France, left tributary of the Dordogne River. Its source is in the south-western Massif Central, near the mountain Plomb du Cantal...
.
The sexes are alike in color, but the female is larger. Immature birds have pale edges on the upperwing coverts and some brownish-grey feathers on the back.
The Black-and-white Hawk-Eagle is hard to confuse with any other bird in its range. The Black-faced Hawk
Black-faced Hawk
The Black-faced Hawk is a species of bird of prey in the Accipitridae family. This low-density species has traditionally been believed to be restricted to Amazon Basin north of the Amazon River, but there are several records south of this river, in, for example, the Brazilian states of Pará and...
(Leucopternis melanops) is very similar in overall coloration, but it is much smaller and has a black tail with a single bold white bar in the middle. The Ornate Hawk-Eagle (Spizaetus ornatus), presumably a very close relative of S. melanoleucus, looks quite similar when young. However, the wings, back and tail are much lighter in young S. ornatus, and they do not have the black eye-ring.
Distribution and ecology
This species occurs from OaxacaOaxaca
Oaxaca , , officially Estado Libre y Soberano de Oaxaca is one of the 31 states which, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided into 571 municipalities; of which 418 are governed by the system of customs and traditions...
to Veracruz
Veracruz
Veracruz, formally Veracruz de Ignacio de la Llave officially Estado Libre y Soberano de Veracruz de Ignacio de la Llave , is one of the 31 states that, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided in 212 municipalities and its capital city is...
in southern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
southwards throughout Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
, with the exception of most of El Salvador
El Salvador
El Salvador or simply Salvador is the smallest and the most densely populated country in Central America. The country's capital city and largest city is San Salvador; Santa Ana and San Miguel are also important cultural and commercial centers in the country and in all of Central America...
and the Pacific coast of Nicaragua
Nicaragua
Nicaragua is the largest country in the Central American American isthmus, bordered by Honduras to the north and Costa Rica to the south. The country is situated between 11 and 14 degrees north of the Equator in the Northern Hemisphere, which places it entirely within the tropics. The Pacific Ocean...
. In South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, it occurs on the Pacific side of the Andes
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...
south to Ecuador
Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
. The bulk of its range extends along the Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...
coast from northern Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
and Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
to the Guianas, and south through eastern Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, Paraguay
Paraguay
Paraguay , officially the Republic of Paraguay , is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to the east and northeast, and Bolivia to the northwest. Paraguay lies on both banks of the Paraguay River, which runs through the center of the...
and Uruguay
Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...
to NE Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, and from there westwards again to Beni
Beni Department
Beni, sometimes El Beni, is a northeastern department of Bolivia, in the lowlands region of the country. It is the second largest department in the country , covering 213,564 square kilometers , and it was created by supreme decree on November 18, 1842 during the administration of General José...
and Santa Cruz
Santa Cruz Department
Santa Cruz, with an area of 370,621 km², is the largest of the nine constituent departments of Bolivia. In the 2001 census, it reported a population of 2,029,471. The capital is the city of Santa Cruz de la Sierra. The state is one of the wealthiest states in Bolivia with huge reserves of...
in NE Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
. A Black-and-white Hawk-Eagle population is also found in the Loreto Region
Loreto Region
Loreto is Peru's northernmost region. Covering almost one-third of Peru's territory, Loreto is by far the nation's largest region and also one of the most sparsely populated ones, due to its remote location in the Amazon Rainforest...
of NE Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
; it is not known in how far this is isolated from the rest of the bird's range. The species is absent from western Amazonia, and it is not common in the lands to the east (e.g. in Minas Gerais
Minas Gerais
Minas Gerais is one of the 26 states of Brazil, of which it is the second most populous, the third richest, and the fourth largest in area. Minas Gerais is the Brazilian state with the largest number of Presidents of Brazil, the current one, Dilma Rousseff, being one of them. The capital is the...
).
Its natural habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s are lowland forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
s of any type, though very dense and humid as well as savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
-like semiarid habitat are not preferred. Habitat fragmentation
Habitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population fragmentation...
is not very well tolerated; though the species prefers a diverse habitat of mixed forest and shrubland, it requires large stands of closed-canopy
Canopy (forest)
In biology, the canopy is the aboveground portion of a plant community or crop, formed by plant crowns.For forests, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms .Sometimes the term canopy is used to refer to the extent...
forest to thrive. Its range does not extend very far into the uplands, but one individual was sighted at an altitude of about 4,000 ft (c.1,200 m) ASL
Above mean sea level
The term above mean sea level refers to the elevation or altitude of any object, relative to the average sea level datum. AMSL is used extensively in radio by engineers to determine the coverage area a station will be able to reach...
in the Buena Vista Nature Reserve in Colombia's Sierra Nevada de Santa Marta
Sierra Nevada de Santa Marta
The Sierra Nevada de Santa Marta is an isolated mountain range apart from the Andes chain that runs through Colombia. Reaching an altitude of 5,700 metres above sea level just 42 km from the Caribbean coast, the Sierra Nevada is the world's highest coastal range...
.
The food of this carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
consists of mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s, toad
Toad
A toad is any of a number of species of amphibians in the order Anura characterized by dry, leathery skin , short legs, and snoat-like parotoid glands...
s, squamates and in particular a wide variety of birds. Among the latter, it is known to prefer tree-living species, such as oropendola
Oropendola
The oropendolas comprise two or three genera of South and Central American passerine birds in the New World blackbird family.All the oropendolas are large birds with pointed bills, and long tails which are always at least partially bright yellow...
s, aracari
Aracari
The aracaris are medium-sized toucans in the genus Pteroglossus. As denoted by the presence of the cedilla on the C , the proper pronunciation is "ahr-uh-SAHR-ee" not "ahr-uh-KAR-ee"....
s, tanager
Tanager
The tanagers comprise the bird family Thraupidae, in the order Passeriformes. The family has an American distribution.There were traditionally about 240 species of tanagers, but the taxonomic treatment of this family's members is currently in a state of flux...
s and cotinga
Cotinga
The cotingas are a large family of passerine bird species found in Central America and tropical South America. Cotingas are birds of forests or forest edges, which mostly eat fruit or insects and fruit. Comparatively little is known about this diverse group, although all have broad bills with...
s. But ground- and waterbirds like tinamou
Tinamou
The tinamous are a family comprising 47 species of birds found in Central and South America. One of the most ancient living groups of bird, they are related to the ratites. Generally ground dwelling, they are found in a range of habitats....
s, chachalaca
Chachalaca
Chachalacas are mainly brown birds from the genus Ortalis. These cracids are found in wooded habitats in far southern United States , Mexico, and Central and South America. They are social, can be very noisy and often remain fairly common even near humans, as their relatively small size makes them...
s, cormorant
Cormorant
The bird family Phalacrocoracidae is represented by some 40 species of cormorants and shags. Several different classifications of the family have been proposed recently, and the number of genera is disputed.- Names :...
s and the highly threatened Brazilian Merganser
Brazilian Merganser
The Brazilian Merganser, Mergus octosetaceus, is a duck in the typical merganser genus.It is one of the six most threatened waterfowl in the world with possibly fewer than 250 birds in the wild and none kept in captivity...
(Mergus octosetaceus) have also been recorded as its prey. The Black-and-white Hawk-Eagle has been known to attack small monkey
New World monkey
New World monkeys are the five families of primates that are found in Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Platyrrhini parvorder and the Ceboidea superfamily, which are essentially synonymous since...
s, though it is not clear with which intent. For as it seems, it has not been recorded to actually kill and eat a monkey.
Its preferred hunting technique is to soar high until it has spotted suitable prey, and then dive down on it, usually right into the forest canopy, but it has also been observed to catch a White Woodpecker
White Woodpecker
The White Woodpecker, Melanerpes candidus, is a species of woodpecker found in South America. This woodpecker is a native of the grasslands of Brazil, Bolivia, Paraguay, Uruguay and Argentina....
(Melanerpes candidus) that had been mobbing
Mobbing behavior
Mobbing in animals is an antipredator behavior which occurs when individuals of a certain species mob a predator by cooperatively attacking or harassing it, usually to protect their offspring. A simple definition of mobbing is an assemblage of individuals around a potentially dangerous predator...
it in mid-air, after launching itself from its perch. It likes to hunt along ridges and forest edges where it can access the canopy-level from an oblique direction rather than just from directly above, and where ground-living prey is also more accessible.
It nests in the forest canopy, building a stick nest high up in exposed trees on ridges and similar locations, from where good hunting grounds can be watched. Detailed observations on its nesting habits are nearly non-existent however. In Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...
, birds started to construct a nest in September, during a dry spell in the rainy season. But the main nesting season may start before the onset of the rainy season as the nesting attempt was abandoned when heavy rains recommenced. The scant other data agrees with this, and at least in Central America the nesting season seems to run from March to June or so.
There is a general lack of information on the Black-and-white Hawk-Eagle's movements and population status. Each bird seems to require a hunting territory of about 3,500 acres (1,400 hectars) at least. While the variety of habitat types in which it is found suggests that it is not particularly susceptible to changes in land use, it is apparently still a rare and local species almost anywhere in its range. The IUCN until 2000 classified it as a Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
species due to the uncertainties surrounding its status, but as no evidence of a marked decline has been found and as the bird is found across a wide range, it was downlisted to a Species of Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
.
Taxonomy and systematics
This species is often placed in the monotypicMonotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
genus Spizastur, but has recently been moved to Spizaetus
Spizaetus
Spizaetus is the typical hawk-eagle birds of prey genus found in the tropics of the Americas. It was however used to indicate a group of tropical eagles that included species occurring in southern and southeastern Asia and one representative of this genus in the rainforests of West Africa. The Old...
e.g. by the American Ornithologists' Union
American Ornithologists' Union
The American Ornithologists' Union is an ornithological organization in the USA. Unlike the National Audubon Society, its members are primarily professional ornithologists rather than amateur birders...
, as it appears that the Ornate Hawk-Eagle (S. ornatus) is its sister taxon. This has created quite some taxonomic confusion, which has largely gone unnoticed however:
Originally, the name Spizaetus melanoleucus was given by Louis Jean Pierre Vieillot
Louis Jean Pierre Vieillot
Louis Jean Pierre Vieillot was a French ornithologist.Vieillot described a large number of birds for the first time, especially those he encountered during the time he spent in the West Indies and North America, and 26 genera established by him are still in use...
to the Black-chested Buzzard-eagle
Black-chested Buzzard-eagle
The Black-chested Buzzard-Eagle is a bird of prey of the hawk and eagle family . It lives in open regions of South America. This species is also known as the Black Buzzard-eagle, Grey Buzzard-eagle or analogously with "eagle" or "eagle-buzzard" replacing "buzzard-eagle", or as the Chilean Blue Eagle...
in 1819, while the Black-and-white Hawk-Eagle had been described in 1816 by the very same scientist as Buteo melanoleucus. The former species was placed in Geranoaetus – also a monotypic genus – in 1844, while the Black-and-white Hawk-Eagle had been moved out of Buteo and into Spizastur a few years earlier.
Thus, the identical specific epithets never came into direct conflict until recently. But the Black-chested Eagle-buzzard's placement in a monotypic genus was always disputed, and several authors treated it in Buteo. However, they overlooked that Buteo melanoleucus was the original name of the Black-and-white Hawk-Eagle and thus as a senior homonym could not be applied to the later-described species. The correct specific name for the Black-chested Eagle-buzzard when placed in Buteo, Buteo fuscescens, was reestablished in the mid-20th century for a short time more by accident than anything else; as most late-20th-century researchers argued for retaining Geranoaetus, this name was dismissed as erroneous and essentially forgotten.
As the Black-and-white Hawk-Eagle has not been placed in Buteo since long, Article 59.3 of the ICZN
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...
Code applies. According to this, a junior homonym replaced before 1961 is not rendered permanently invalid (as junior homonyms usually are) if "the substitute name is not in use" – which has been the case after Amadon's 1963 revision. Hence, in this case the scientific name Buteo melanoleucus can apply to the Black-chested Eagle-buzzard, even though the Black-and-white Hawk-Eagle was described under exactly that name earlier, while the senior homonym melanoleucus still applies to the latter species when placed in Spizaetus according to the usual ICZN rules. Consequently, the proper name to use for each bird has through a number of coincidences become the senior synonym of the other species.