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.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
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.
CITES: no special status
IUCN Red List of Threatened Species: least concern
There are no known adverse effects of crested serpent eagles on humans.
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.
Positive Impacts: controls pest population
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.
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.
Animal Foods: birds; mammals; amphibians; reptiles
Primary Diet: carnivore (Eats terrestrial vertebrates)
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.
Biogeographic Regions: oriental (Native ); indian ocean (Native )
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.
Average elevation: 1900 m.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: savanna or grassland ; forest ; rainforest
Wetlands: marsh
Other Habitat Features: agricultural ; riparian
The lifespan and longevity of crested serpent eagles in the wild is unknown, however they may live up to 50 years in captivity.
Range lifespan
Status: captivity: 50 (high) years.
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.
Range mass: 420 to 1800 g.
Range length: 55 to 76 cm.
Range wingspan: 109 to 169 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
Crested serpent eagles are apex predators and have no known predators.
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.
Mating System: monogamous
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.
Breeding interval: Crested serpent eagles breed once yearly.
Breeding season: The breeding season of crested serpent eagles corresponds with dry season. Depending on the region, it occur anytime between December and May.
Range eggs per season: 1 to 2.
Average time to hatching: 35 days.
Average fledging age: 2 months.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
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.
Parental Investment: altricial ; male parental care ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
The crested serpent eagle (Spilornis cheela) is a medium-sized bird of prey that is found in forested habitats across tropical Asia. Within its widespread range across the Indian Subcontinent, Southeast Asia and East Asia, there are considerable variations and some authorities prefer to treat several of its subspecies as completely separate species.[2] In the past, several species including the Philippine serpent eagle (S. holospila), Andaman serpent eagle (S. elgini) and South Nicobar serpent eagle (S. klossi) were treated as subspecies of the Crested serpent eagle. All members within the species complex have a large looking head with long feathers on the back of the head giving them a maned and crested appearance. The face is bare and yellow joining up with the ceres while the powerful feet are unfeathered and heavily scaled. They fly over the forest canopy on broad wings and tail have wide white and black bars. They call often with a loud, piercing and familiar three or two-note call. They often feed on snakes, giving them their name and are placed along with the Circaetus snake-eagles in the subfamily Circaetinae.
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This medium-large, dark brown eagle is stocky, with rounded wings and a short tail. Its short black and white fan-shaped nuchal crest gives it a thick-necked appearance. The bare facial skin and feet are yellow. The underside is spotted with white and yellowish-brown. When perched the wing tips do not reach until the tail tip. In soaring flight, the broad and paddle-shaped wings are held in a shallow V. The tail and underside of the flight feathers are black with broad white bars. Young birds show a lot of white on the head.[3][4] The tarsus is unfeathered and covered by hexagonal scales. The upper mandible does not have an overhanging festoon to the tip.[5]
This species of serpent eagle manifests an unusual amount of size variation across its assorted subspecies. Total length of fully-grown crested serpent eagles can vary from 41 to 75 cm (16 to 30 in) and wingspan can vary from 89 to 169 cm (2 ft 11 in to 5 ft 7 in).[6][7][8] The largest proportioned race appears to be the nominate, S. c. cheela, with a wing chord of 468 to 510 mm (18.4 to 20.1 in) in males and 482 to 532 mm (19.0 to 20.9 in) in females, tail lengths of 295 to 315 mm (11.6 to 12.4 in) and tarsus length of 100 to 115 mm (3.9 to 4.5 in). In comparison, S. c. minimus, probably the smallest race, has a wing chord of 257 to 291 mm (10.1 to 11.5 in) in males and 288 to 304 mm (11.3 to 12.0 in) in females, tail lengths of around 191 mm (7.5 in) and tarsal length of around 76 mm (3.0 in).[8] Weights are more fitfully reported but are estimated to vary perhaps threefold between assorted races.[8][9] In very small subspecies such as S. c. asturinus body masses were found to be 420 g (15 oz) in a male and 565 g (19.9 oz) in a female.[8] In S. c. palawanesis, body mass was reported at 688 g (24.3 oz) in males and 853 g (30.1 oz) in females.[10] Serpent eagles from Borneo, S. c. pallidus, may between 625 and 1,130 g (22.0 and 39.9 oz).[8][11] Mainland forms are typically larger but a weight of 900 g (32 oz) was cited for the fairly small mainland race, S. c. burmanicus.[12] In the race S. c. hoya, weights were much higher, averaging 1,207 g (42.6 oz); meanwhile, in the same race, 8 males averaged 1,539 g (54.3 oz) and 6 females averaged 1,824 g (64.3 oz).[13][14] In some cases, serpent eagles may attain estimated weights of approximately 2,300 g (81 oz).[15]
The crested serpent eagle is placed along with the snake eagles of the genus Circaetus in the subfamily Circaetinae.[16]
The nominate subspecies has a black throat while the peninsular Indian form has a brownish throat. There are clinal latitudinal variations, with size decreasing southward.[3] The small islands taxa are generally smaller in size than the taxa from the Asian mainland/larger islands in a phenomenon termed as insular dwarfism.[2][17] Within its widespread range across tropical Asia, 21 subspecies have been proposed:[2]
The remaining sub-species are all restricted to smaller islands:
The last seven (with English names in brackets) are sometimes treated as separate species.[2] Although the crested serpent eagle remains widespread and fairly common overall, some of the taxa that are restricted to small islands are believed to have relatively small populations that likely are in the hundreds.[2]
The rarest is probably the Bawean serpent eagle with a declining population of about 26–37 pairs, which makes it critically endangered.[18][17][19][20]
The crested serpent eagle is a reptile eater which hunts over forests, often close to wet grassland,[21] for snakes and lizards. It has also been observed to prey on birds, amphibians, mammals, fishes, termites and large earthworms.[22][23] It is found mainly over areas with thick vegetation both on the low hills and the plains. This species is a resident species, but in some parts of their range they are found only in summer.[3][24]
The call is a distinctive Kluee-wip-wip with the first note being high and rising. They call a lot in the late mornings from their perches where they spend a lot of time and they rise on thermals in the mornings.[3] In southern Taiwan, males have a larger home range than females. Males on average had a home range of 16.7 km2 while females used about 7 km2.[25] When alarmed, they erect the crest and the head appears large and framed by the ruff.[5] They will sometimes follow snakes on the ground.[26] They roost in the interiors of trees with dense foliage.[27] A radio-telemetric study of the species in Taiwan found that the birds spend 98% of the day perched and usually finding food in the morning hours. They appear to use a sit and wait foraging strategy.[28]
The breeding season begins in late winter when they start courting and establishing territories. The eggs are laid in early summer. Old nests are often refurbished and reused in India but a study in Penang found them to build fresh nests each year.[29] A study in India found that most nests were built along riverine trees. The nest is a large platform built high on a tree. Both birds in a pair build the nest but the female alone incubates. The male guards when the female forages. In central India, the Terminalia tomentosa is often used while Terminalia bellirica and Dalbergia latifolia was often used in southern India.[22] In Penang, the nest trees were typically large and isolated from other trees with lot of room for the birds to fly in and out. The nests are lined with green leaves collected from nearby and are placed facing down on the nest floor.[26][29] The usual clutch is one egg but two are sometimes laid and only a single chick is successfully raised in a season. When eggs are lost, a replacement is laid two to seven weeks later. The eggs hatch after about 41 days and the young fledge after about two months. Nests are defended by the parents.[5][30][31][32]
Several species of endoparasitic nematodes have been recovered from the intestines of crested serpent eagles, including Madelinema angelae.[33][34] Avian pox virus infections which cause warts on the face have been observed in a wild bird living in Taiwan.[35] A number of ectoparasitic bird lice have been described from the species including Kurodaia cheelae.[36] In Penang, it was found that cinereous tits (Parus cinereus ambiguus) tended to nest close to nesting crested serpent eagles, presumably due to safety from predators like crows that may be driven off by the eagles. They have also been found to visit the nests of the eagles to collect fur from the remains of dead mammal prey.[29]
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{{cite journal}}: CS1 maint: multiple names: authors list (link) The crested serpent eagle (Spilornis cheela) is a medium-sized bird of prey that is found in forested habitats across tropical Asia. Within its widespread range across the Indian Subcontinent, Southeast Asia and East Asia, there are considerable variations and some authorities prefer to treat several of its subspecies as completely separate species. In the past, several species including the Philippine serpent eagle (S. holospila), Andaman serpent eagle (S. elgini) and South Nicobar serpent eagle (S. klossi) were treated as subspecies of the Crested serpent eagle. All members within the species complex have a large looking head with long feathers on the back of the head giving them a maned and crested appearance. The face is bare and yellow joining up with the ceres while the powerful feet are unfeathered and heavily scaled. They fly over the forest canopy on broad wings and tail have wide white and black bars. They call often with a loud, piercing and familiar three or two-note call. They often feed on snakes, giving them their name and are placed along with the Circaetus snake-eagles in the subfamily Circaetinae.
