Congo serpent eagle

The Congo serpent eagle (Circaetus spectabilis) is a species of bird of prey in the family Accipitridae. This species is distributed across the African tropical rainforest, including upper and lower Guinean forests. This serpent eagle specializes in hunting in these forests' dark understories. It has two subspecies, the nominate subspecies Circaetus spectabilis spectabilis and Circaetus spectabilis batesi. 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 C. 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.

This hawk is a medium-sized, slender species with short, rounded wings and a long, rounded tail. It is 54 to 60 centimeters (21 to 24 in) long, with the tail contributing 24.5 to 26.8 centimeters (9.6 to 10.6 in). The wingspan is 94 to 106 centimeters (37 to 42 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 beak 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.

C. s. batesi is similar to the nominate subspecies, but is browner and paler on the back while the spots on C. s. spectabilis's 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.