Congo Serpent-eagle
Encyclopedia
The Congo Serpent Eagle (Dryotriorchis spectabilis) is a species of bird of prey
in the family Accipitridae
, and is placed in the monotypic
genus
Dryotriorchis. This species is found in western and central Africa, with its range stretching from Sierra Leone south to Angola and west to the Democratic Republic of the Congo. It occurs in upper and lower Guinean forests
, which are dense rainforests. This serpent eagle specializes in hunting in these forests’ dark understories. It has two subspecies, the nominate subspecies Dryotriorchis spectabilis spectabilis and Dryotriorchis spectabilis batesi. Though monotypic, it appears to be very closely related to Circaetus
. This hawk is a medium-sized bird with distinctive short, rounded wings and a long, rounded tail. It is varying shades of brown on its back and has a slight crest. Its breast is white with variable amounts of a rufous wash and, in the nominate subspecies, is covered in round, blackish spots. The subspecies D. s. batesi only has these dots on its flanks. The Congo Serpent Eagle closely resembles Cassin's Hawk Eagle, and some ornithologists believe that this likeness is a rare example of avian mimicry. It is a very vocal raptor, and often is one of the most heard species in its habitat.
This serpent eagle feeds on snakes, chameleons, and toads, and hunts these species by dropping onto them from a perch in the understory. Its excellent eyesight enables it to hunt in the dark forest. Very little is known about its breeding habits, though it is suspected to breed from June to December. The Congo Serpent Eagle is listed as a species of Least Concern
due to its large range and population. This species has been kept as a pet.
as Astur spectabilis from a specimen collected near Elmina
, Ghana. Schlegel published his description in Nederlandsch Tijdschrift voor De Dierkunde and placed this species within the goshawk
s. In 1874 George Ernest Shelley
, who had access to more specimens, realized that this bird wasn't a goshawk and moved the species into its own monotypic
genus
, Dryotriorchis. Dryotriorchis is a distinct genus due to its short wings, long tail, short crest, and oval nostrils. It is believed that the genus is more closely related to Circaetus
than Terathopius, and it is possibly a link between these and the Asian genus Spilornis
. The syrinx morphology is distinctly like those of accipiter hawks but shows similarities to features found in Nisaetus
. Two subspecies
are known: the nominate subspecies Dryotriorchis spectabilis spectabilis and D. s. batesi. D. s. batesi was originally described as a separate species, Dryotriorchis batesi, by Richard Bowdler Sharpe
in 1904 due to its unspotted breast. Sharpe named the subspecies in honor of G. L. Bates
, who shipped him specimens from Cameroon. This species is also known as the West African Serpent Eagle and the African Serpent-eagle.
The Congo Serpent Eagle is superficially similar in plumage and size to Cassin's Hawk Eagle, which has an overlapping range with the serpent eagle. It has been suggested that the Congo Serpent Eagle evolved to mimic the Cassin's Hawk Eagle, which could give the serpent eagle several advantages, possibly including the ability to trick its reptilian prey into not fleeing, lowering its own predation, and/or minimizing mobbing by birds through its resemblance to a predator of birds. D. s. spectabilis more closely resembles the immature Cassin's Hawk Eagle, while D. s. batesi resembles the adult. This is one of very few suspected examples of avian mimicry.
is short but deep. It also has a black median streak. The bird's underparts are white with variable amounts of rufous wash and a number of large, round blackish spots. The serpent eagle's thighs are barred sepia-brown and white, while the undertail is white. The underwing is largely white with some black spots and brown coloration. The tail is light brown, with five to six broad black bars. The claws are short and sharp, while the legs are yellow. Sexes are similar, though the female averages about three percent larger than the male. Immatures have a white crown and mantle, while the upper back has rounded brown or black spots that vanish as the bird ages. The wings and tail are greyish-brown and paler than those of the adults and are more darkly barred.
D. s. batesi is similar to the nominate subspecies, but is browner and paler on the back while the spots on D. s. spectabiliss chest only appear on this subspecies' flanks. The immature does possess a spotted chest, with the spots vanishing as the bird ages.
This is a very vocal raptor and is one of the most frequently heard birds of prey in its range. It makes a cat-like meowing sound as well as a low, mournful, nasal "cow-cow-cow" at intervals over extended periods of time. When heard over a large distance, some ornithologists have compared its call to that of a turaco
.
from southern Cameroon through Gabon and western Uganda. Its range covers 2880000 square kilometres (1,111,974.2 sq mi). The species lives in dense primary forest below 900 metres (2,952.8 ft) in elevation in the dark understory. As it is adapted for dense forest, it is not well-adapted for secondary forests and plantations. The Congo Serpent Eagle does not migrate, though it is unknown if it is locally nomadic.
s, toads, and potentially small mammals. It hunts by dropping to the ground from its perch in the understory, where it may strike its prey repeatedly with its feet; this serpent eagle may also grab prey from the foliage while hunting. Its large eyes enable this species to hunt in low light, though it is diurnal. Studies on the species' eyes have shown that they have about two times the visual resolution of a human's. It may breed from October to December in Gabon and from June to November in the Democratic Republic of the Congo.
due to its large population of over 10,000 adults and large range of 2880000 square kilometres (1,111,974.2 sq mi). This species has been kept as a pet and in the 1970s was available from some pet shops. The Congo Serpent Eagle has been depicted on postage stamps from the Democratic Republic of the Congo and Tanzania.
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....
in the family 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...
, and is placed in the monotypic
Monotypic
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
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Dryotriorchis. This species is found in western and central Africa, with its range stretching from Sierra Leone south to Angola and west to the Democratic Republic of the Congo. It occurs in upper and lower Guinean forests
Lower Guinean forests
The Lower Guinean forests is region of coastal tropical moist broadleaf forest extending along the coast of the Gulf of Guinea from eastern Benin through Nigeria and Cameroon....
, which are dense rainforests. This serpent eagle specializes in hunting in these forests’ dark understories. It has two subspecies, the nominate subspecies Dryotriorchis spectabilis spectabilis and Dryotriorchis spectabilis batesi. Though monotypic, it appears to be very closely related to Circaetus
Circaetus
Circaetus, the snake eagles, is a genus of medium-sized eagles in the bird of prey family Accipitridae which also includes many other diurnal raptors such as buzzards and harriers....
. This hawk is a medium-sized bird with distinctive short, rounded wings and a long, rounded tail. It is varying shades of brown on its back and has a slight crest. Its breast is white with variable amounts of a rufous wash and, in the nominate subspecies, is covered in round, blackish spots. The subspecies D. s. batesi only has these dots on its flanks. The Congo Serpent Eagle closely resembles Cassin's Hawk Eagle, and some ornithologists believe that this likeness is a rare example of avian mimicry. It is a very vocal raptor, and often is one of the most heard species in its habitat.
This serpent eagle feeds on snakes, chameleons, and toads, and hunts these species by dropping onto them from a perch in the understory. Its excellent eyesight enables it to hunt in the dark forest. Very little is known about its breeding habits, though it is suspected to breed from June to December. The Congo Serpent Eagle is listed as 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...
due to its large range and population. This species has been kept as a pet.
Taxonomy
The Congo Serpent Eagle was first described in 1863 by Hermann SchlegelHermann Schlegel
Hermann Schlegel was a German ornithologist and herpetologist.-Early life and education:Schlegel was born at Altenburg, the son of a brassfounder. His father collected butterflies, which stimulated Schlegel's interest in natural history...
as Astur spectabilis from a specimen collected near Elmina
Elmina
Elmina, is a town in the Central Region, situated on a south-facing bay on the Atlantic Ocean coast of Ghana, about 12 km west of Cape Coast...
, Ghana. Schlegel published his description in Nederlandsch Tijdschrift voor De Dierkunde and placed this species within the goshawk
Accipiter
The genus Accipiter is a group of birds of prey in the family Accipitridae, many of which are named as goshawks and sparrowhawks. They can be anatomically distinguished from their relatives by the lack of a procoracoid foramen. Two small and aberrant species usually placed here do possess a large...
s. In 1874 George Ernest Shelley
George Ernest Shelley
Captain George Ernest Shelley was an English geologist and ornithologist. He was a nephew of the poet Percy Bysshe Shelley....
, who had access to more specimens, realized that this bird wasn't a goshawk and moved the species into its own monotypic
Monotypic
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
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, Dryotriorchis. Dryotriorchis is a distinct genus due to its short wings, long tail, short crest, and oval nostrils. It is believed that the genus is more closely related to Circaetus
Circaetus
Circaetus, the snake eagles, is a genus of medium-sized eagles in the bird of prey family Accipitridae which also includes many other diurnal raptors such as buzzards and harriers....
than Terathopius, and it is possibly a link between these and the Asian genus Spilornis
Spilornis
Spilornis is a genus of bird of prey in the family Accipitridae. As adults all have dark crowns, and bright yellow eyes and cere. These medium-sized raptors are found in forests of southern Asia and are known as serpent-eagles; an English name shared with two African species from the genera...
. The syrinx morphology is distinctly like those of accipiter hawks but shows similarities to features found in Nisaetus
Nisaetus
Nisaetus is a genus of eagles found mainly in tropical Asia. They were earlier placed within the genus Spizaetus but molecular studies show that the Old World representatives were closer to the genus Ictinaetus than to the New World Spizaetus...
. Two subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
are known: the nominate subspecies Dryotriorchis spectabilis spectabilis and D. s. batesi. D. s. batesi was originally described as a separate species, Dryotriorchis batesi, by Richard Bowdler Sharpe
Richard Bowdler Sharpe
Richard Bowdler Sharpe was an English zoologist.-Biography:Sharpe was born in London and studied at Brighton College, The King's School, Peterborough and Loughborough Grammar School. At the age of sixteen he went to work for Smith & Sons in London...
in 1904 due to its unspotted breast. Sharpe named the subspecies in honor of G. L. Bates
George Latimer Bates
George Latimer Bates , LL.D., M.B.O.U. was an American naturalist.Bates studied at Knox College, Galesburg and at the Chicago Theological Seminary and in 1895 visited West Africa and lived in the south east Cameroon, making a living by farming...
, who shipped him specimens from Cameroon. This species is also known as the West African Serpent Eagle and the African Serpent-eagle.
The Congo Serpent Eagle is superficially similar in plumage and size to Cassin's Hawk Eagle, which has an overlapping range with the serpent eagle. It has been suggested that the Congo Serpent Eagle evolved to mimic the Cassin's Hawk Eagle, which could give the serpent eagle several advantages, possibly including the ability to trick its reptilian prey into not fleeing, lowering its own predation, and/or minimizing mobbing by birds through its resemblance to a predator of birds. D. s. spectabilis more closely resembles the immature Cassin's Hawk Eagle, while D. s. batesi resembles the adult. This is one of very few suspected examples of avian mimicry.
Description
This hawk is a medium-sized, slender species with short, rounded wings and a long, rounded tail. It is 54 to 60 cm (21.3 to 23.6 in) long, with the tail contributing 24.5 to 26.8 cm (9.6 to 10.6 in). The wingspan is 94 to 106 cm (37 to 41.7 in) across. The adult of the nominate subspecies, Dryotriorchis spectabilis spectabilis, has a blackish-brown crown and upper neck while the sides of the neck and a broad collar are a dark rufous-brown. The feathers on the top of the head are slightly pointed, giving this species a hint of a crest. The remaining upperparts are a dark chocolate brown. The cheeks are light brown while the throat is buffy white with streaks. The eyes are large and dark brown or grey in females and yellow in males while the beakBeak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
is short but deep. It also has a black median streak. The bird's underparts are white with variable amounts of rufous wash and a number of large, round blackish spots. The serpent eagle's thighs are barred sepia-brown and white, while the undertail is white. The underwing is largely white with some black spots and brown coloration. The tail is light brown, with five to six broad black bars. The claws are short and sharp, while the legs are yellow. Sexes are similar, though the female averages about three percent larger than the male. Immatures have a white crown and mantle, while the upper back has rounded brown or black spots that vanish as the bird ages. The wings and tail are greyish-brown and paler than those of the adults and are more darkly barred.
D. s. batesi is similar to the nominate subspecies, but is browner and paler on the back while the spots on D. s. spectabiliss chest only appear on this subspecies' flanks. The immature does possess a spotted chest, with the spots vanishing as the bird ages.
This is a very vocal raptor and is one of the most frequently heard birds of prey in its range. It makes a cat-like meowing sound as well as a low, mournful, nasal "cow-cow-cow" at intervals over extended periods of time. When heard over a large distance, some ornithologists have compared its call to that of a turaco
Turaco
The turacos make up the bird family Musophagidae , which includes plantain-eaters and go-away-birds. In southern Africa both turacos and go-away-birds are commonly known as louries. They are semi-zygodactylous - the fourth toe can be switched back and forth...
.
Distribution and habitat
The Congo Serpent Eagle lives in southern Sierra Leone and Guinea, Liberia, and southern Côte d'Ivoire and Ghana. It is also found in southern Nigeria and the Central African Republic south through northern and eastern Democratic Republic of the Congo in the east and through Gabon into the northern Republic of the Congo in the west with an isolated population in northern Angola. D. s. spectabilis is found in upper Guinean forests from Liberia to northern Cameroon, while D. s. batesi is found in lower Guinean forestsLower Guinean forests
The Lower Guinean forests is region of coastal tropical moist broadleaf forest extending along the coast of the Gulf of Guinea from eastern Benin through Nigeria and Cameroon....
from southern Cameroon through Gabon and western Uganda. Its range covers 2880000 square kilometres (1,111,974.2 sq mi). The species lives in dense primary forest below 900 metres (2,952.8 ft) in elevation in the dark understory. As it is adapted for dense forest, it is not well-adapted for secondary forests and plantations. The Congo Serpent Eagle does not migrate, though it is unknown if it is locally nomadic.
Ecology and behavior
Little is known about this species' behavior. The Congo Serpent Eagle lives in the understory of its habitat and occasionally perches on lower boughs in tall trees. It lives either alone or in pairs. This species is known to hunt snakes, lizards, especially chameleonChameleon
Chameleons are a distinctive and highly specialized clade of lizards. They are distinguished by their parrot-like zygodactylous feet, their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues, their swaying gait, the possession by many of a...
s, toads, and potentially small mammals. It hunts by dropping to the ground from its perch in the understory, where it may strike its prey repeatedly with its feet; this serpent eagle may also grab prey from the foliage while hunting. Its large eyes enable this species to hunt in low light, though it is diurnal. Studies on the species' eyes have shown that they have about two times the visual resolution of a human's. It may breed from October to December in Gabon and from June to November in the Democratic Republic of the Congo.
Relationship with humans
Currently, the Congo Serpent Eagle's population is dwindling due to deforestation. However, it is listed as a species of Least ConcernLeast 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...
due to its large population of over 10,000 adults and large range of 2880000 square kilometres (1,111,974.2 sq mi). This species has been kept as a pet and in the 1970s was available from some pet shops. The Congo Serpent Eagle has been depicted on postage stamps from the Democratic Republic of the Congo and Tanzania.