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

By Thomas Michal

Geographic Range

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)

Habitat

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)

  • Average elevation
    1900 m
    6233.60 ft

Physical Description

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)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    420 to 1800 g
    14.80 to 63.44 oz
  • Range length
    55 to 76 cm
    21.65 to 29.92 in
  • Range wingspan
    109 to 169 cm
    42.91 to 66.54 in

Reproduction

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)

  • 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

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)

  • 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

Lifespan/Longevity

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)

  • Range lifespan
    Status: captivity
    50 (high) years

Behavior

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)

Communication and Perception

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)

Food Habits

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)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles

Predation

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

Ecosystem Roles

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)

Economic Importance for Humans: Positive

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

Economic Importance for Humans: Negative

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

Conservation Status

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)

Contributors

Thomas Michal (author), Florida State University, Emily DuVal (editor), Florida State University, Rachelle Sterling (editor), Special Projects.

Glossary

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

marsh

marshes are wetland areas often dominated by grasses and reeds.

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nomadic

generally wanders from place to place, usually within a well-defined range.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

"Crested Serpent Eagle (Spilornis cheela)" (On-line). National Zoological Park. Accessed February 12, 2010 at http://nzpnewdelhi.gov.in/crested_serpent_eagle.htm.

Del Hoyo, J., A. Elliott, J. Sargatal. 1994. Crested Serpent Eagle. Pp. 134 in J Del Hoyo, A Elliott, J Sargatal, eds. Handbook of the Birds of the World, Vol. 2. Barcelona: Lynx Edicions.

Ferguson-Lees, J., D. Christie. 2005. Crested Serpent Eagle. Pp. 136 in J Ferguson-Lees, ed. raptors of the World: A Field Guide. London: Christopher Help.

Hume, A. 1890. Spilornis cheela. Pp. 153 in A Hume, ed. The Nests and Eggs of the Indian Birds, Vol. 3. London: Taylor and Francis.

Kennedy, R., P. Gonzales, E. Dickinson, H. Miranda Jr, T. Fisher. 2000. Crested Serpent Eagle. Pp. 60 in R Kennedy, ed. A Gide to the Birds of the Phillipinnes. Oxford: Oxford University Press.

Nijman, S., S. nav Balen. 2000. Breeding Biology of the javan Hawk-eagle Spizaetus Bartelsi in West Java, Indonesia. Emu, 100: 125.

No Author Provided, 2009. "Species factsheet: Spilornis cheela" (On-line). BirdLife International. Accessed February 12, 2010 at http://www.birdlife.org.

Ueta, M., J. Minton. 1996. Habitat Preference of the Crested Serpent Eagle in Southern Japan. Journal of Raptor Research, 30/2: 99.

Wells, D. 1999. Crested Serpent Eagle. Pp. 160 in D Wells, ed. The birds of the Thai-Malay Peninsula: covering Burma and thailand south of the leventh parallel, peninsular Malaysia and Singapore, Vol. 1. San Diego, California: AP natural World/Academic Press.

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