Spilornis cheela
crested serpent eagle
(Also: crested serpent-eagle)

Crested serpent eagles (Spilornis cheela) are found throughout much of the Oriental region. In India, Crested serpent eagles can be found from the lower Himalayas to Sri Lanka and the Andamans. Further east they can be found in Southeast Tibet and Southeast China south of the Changiang valley. Outside of mainland Asia, they can be found on the Greater Sunda islands, Bali and the Philippines. (Wells, 1999)

Crested serpent eagles can occur in many different habitats. They prefer the edges of forests where they can soar and effectively hunt. They can inhabit dry to wet forests, tea plantations, wooded savannas and mangroves. They only occasionally enter forest interiors because their size makes maneuvering difficult in thickly wooded habitats. They can tolerate a great deal of disturbance to their habitat, and are found primarily near secondary forests, but they must have some kind of forested area in which to hunt and make a nest. Crested serpent eagles can be found at altitudes of 1900 m. (Del Hoyo, et al., 1994; Hume, 1890; Wells, 1999)

Crested serpent eagles are medium-sized raptors. They range in length from 55 to 76 cm, and their wingspan ranges from 109 to 169 cm. They can weigh anywhere from 420 to 1800 g. When perched, an adult appears overall dark brown with an almost black 'hood' on the head and neck. The breast and belly are brown with white mottling. The crest is black with some white flecks is very prominent when raised. In flight, their underside is brown with a distinctive single, broad, pale band across the tail and wings. They hold their wings forward in a shallow V shape. The legs, eyes, and skin around the eyes and beak (lores) are yellow and bare. Juveniles are distinguished by a much more white plumage, especially around the head. Sexes have very similar plumage. (Del Hoyo, et al., 1994; Ferguson-Lees and Christie, 2005; Wells, 1999)

Crested serpent eagles mate in monogamous pairs and remain in pairs throughout the year. Courtship displays consist of pairs soaring and calling together. These courtship flights may include rolling and wing vibrating. (Del Hoyo, et al., 1994)

The breeding season of crested serpent eagles depends upon the area they live. They prefer to initiate breeding during the dry season. In Southern India they lay eggs between December and March; in Northern India and Sri Lanka they lay between February and May. Their nests are usually found midway in tall trees close to a source of water such as a stream. Their nests range from 1 to 2 feet in diameter, and they are composed of large twigs and stems, usually from the tree that the nest is built on. The nest is lined with smaller twigs, and fresh picked leaves. They frequently nest in the same general area through multiple breeding seasons, but not always in the same nest.

Only one egg has ever been documented in a nest, but pairs tending to two chicks have been reported. Incubation lasts for an average of 35 days. Chicks begin to develop feathers at around 21 days old, and are able to fledge 2 months after hatching. (Del Hoyo, et al., 1994; Hume, 1890; Wells, 1999)

Both the male and female crested serpent eagles will participate in nest construction, however only the female will incubate the egg. Chicks are born altricial without feathers and with eyes closed. The helpless chicks rely on both parents for incubation and feeding. Chicks fledge after 2 months, and are often seen soaring with adults for some time. (Del Hoyo, et al., 1994)

The lifespan and longevity of crested serpent eagles in the wild is unknown, however they may live up to 50 years in captivity. (Del Hoyo, et al., 1994)

Crested serpent eagles are diurnal and non-migratory. They can often be seen soaring over a territory in pairs regardless of season. When not hunting, crested serpent eagles spend a lot of time perched at the edge of a forest surveying their territory. The Japanese race is always found in very close proximity to forest edges or on wet marshland. (Del Hoyo, et al., 1994; Ferguson-Lees and Christie, 2005; Ueta and Minton, 1996; Wells, 1999)

Crested serpent eagles communicate with one another using vocal cues and aerial displays. Their courtship display is fairly complex involving multiple diving runs and mutual soaring with the head and tail feathers raised. They can often be seen soaring over a forest making a distinctive call. There is some geographical variation in the call, but it tends to be a shrill three-note “kluee-wip-wip.” Crested serpent eagles raise their crest when alarmed. Like all birds, they perceive the environment through visual, auditory, tactile, and chemical stimuli. (Del Hoyo, et al., 1994; Wells, 1999)

Crested serpent eagles are very adaptable carnivores. They prey primarily on snakes, as their name implies, and they are not limited to the non-venomous species. They also eat many different kinds of small mammals, monkeys, and birds. They will hunt either from a stationary perch or while soaring. (Del Hoyo, et al., 1994; Ferguson-Lees and Christie, 2005; Kennedy, et al., 2000)

Crested serpent eagles are apex predators and have no known predators.

Crested serpent eagles are apex predators. As such, they are a good indicator of ecosystem health. They are likely important in controlling snake populations since they are their main source of food. They also likely play a role in controlling the numbers of other small mammals and reptiles that they consume. (Del Hoyo, et al., 1994)

Crested serpent eagles eat a significant amount of snakes, including species harmful to humans. They also eat small rodents that can have adverse effects on crop production.

There are no known adverse effects of crested serpent eagles on humans.

Crested serpent eagles are not globally threatened and on most lists they are of least concern. In some areas of India they are a frequent sight and considered common.

However, analysis of isolated island populations may produce unique subspecies. Some of the island races may actually be unique species or sub-species that are critically endangered. The Japanese sub-population on Irimote and Ishigake islands are very threatened due to habitat destruction. On mainland habitats, they are in little danger especially because of their adaptability to disturbed habitats. (Del Hoyo, et al., 1994; Ueta and Minton, 1996)