Overview

Comprehensive Description

Summary

"A medium sized bird of prey with brown above and white with brown barring below. Some sub-species have a crest of four feathers. It is called """"changeable"""" as some sub-species are dimorphic."
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Physical Description

Morphology

"A relatively slender, medium -large raptor with brown above and white below with black longitudinal streaks on throat and chocolate streaks on breast. In some sub-species there is a crest of four feathers projecting behind the head. Sexes are alike but males are smaller than females."
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Size

Larger than a black kite.
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Ecology

Habitat

Habitat and Ecology

Systems
  • Terrestrial
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General Habitat

often sighted singly in open woodland.
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Life History and Behavior

Behavior

Behaviour

"They are generally seen, perched upright on tall trees keeping a lookout for prey. The prey consists of junglefowl, pheasants, hares and other small animals which when sighted, the bird swoops upon and carries away in its talons."
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Reproduction

The nesting season is from December to April. The nest is a platform of sticks lined with green leaves on high forest trees. Usually a single egg is laid.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Spizaetus cirrhatus

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Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2013

Assessor/s
BirdLife International

Reviewer/s
Butchart, S.

Contributor/s

Justification
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size has not been quantified, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

History
  • 2012
    Least Concern
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Red List Category & Criteria: Least Concern ver 3.1
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Population

Population
The global population size has not been quantified, but the species is described as common to uncommon (Ferguson-Lees and Christie 2001).

Population Trend
Decreasing
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Wikipedia

Changeable hawk-eagle

The changeable hawk-eagle or crested hawk-eagle (Nisaetus cirrhatus) is a bird of prey species of the family Accipitridae. It was formerly placed in the genus Spizaetus, but studies pointed to the group being paraphyletic resulting in the Old World members being placed in Nisaetus (Hodgson, 1836) and separated from the New World species.[2]

Changeable hawk-eagles breed in the Indian subcontinent, mainly in India and Sri Lanka, and from the southeast rim of the Himalaya across Southeast Asia to Indonesia and the Philippines. This is a bird occurring singly (outside mating season) in open woodland, although island forms prefer a higher tree density. It builds a stick nest in a tree and lays a single egg.

Description[edit]

The changeable hawk-eagle is a medium-large raptor at about 60–72 centimetres (24–28 in) in length with a 127–138 centimetres (50–54 in) wingspan, and a weight ranging from 1.2 to 1.9 kg.[3] It is a relatively slender forest eagle with some subspecies (especially limnaetus) being dimorphic giving the name of "Changeable". This, and also a complicated phylogeny further complicates precise identification.

Normally brown above; white below with barring on the undersides of the flight feathers and tail; black longitudinal streaks on throat and chocolate streaks on breast. Some subspecies have a crest of four feathers, but this is all but absent in others. The sexes are quite similar in their plumage, but males are about 15% smaller than females.[4] The underparts and head of juveniles are whitish or buff with few dark streaks.[4]

The wings are long and parallel-sided, and are held flat in flight, which helps to distinguish this species from the similar mountain hawk-eagle. In overhead flight, comparatively rounded wings (upturned at tip), longish tail, white body (spotted with brown) and grey underside of wings (streaked and spotted) are leading pointers.

A crestless rare dark morph in flight from Sunderbans National Park, West Bengal, India
Call of changeable hawk-eagle recorded in Parambikulam

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Call is a loud, high-pitched ki-ki-ki-ki-ki-ki-ki-ki-kee, beginning short, rising in crescendo and ending in a scream.

Ecology[edit]

Changeable hawk-eagles eat mammals, birds and reptiles. They like to keep a sharp lookout perched bolt upright on a bough amongst the canopy foliage of some high tree standing near a forest clearing (see photos). There they wait for junglefowl, pheasants, hares and other small animals coming out into the open. The bird then swoops down forcefully, strikes, and bears the prey away in its talons (Ali & Daniel1983).

Nesting[edit]

  • Season: December to April.
  • Nest: a large stick platform lined with green leaves, high up in a forest tree.
  • Eggs: a single one, greyish white, unmarked or with faint specks and blotches of light reddish at the broad end.

Systematics[edit]

The Flores hawk-eagle has traditionally been treated as a subspecies of the changeable hawk-eagle, but it is now often treated as a separate species, N. floris.[5]

Two distinct groups exist in the changeable hawk-eagle; one with crests and one without or with hardly visible crests. Dark morphs exist for some populations.[6]

Changeable hawk-eagle

Gangetic plain southwards throughout India
Crested, no dark morph.
Sri Lanka (possibly also Travancore)
Smaller than nominate, crest proportionally longer on average. Apparently no dark morph.

Crestless changeable hawk-eagle

Nepal, NE India, via Burma and Malay Peninsula along Wallace Line to Philippines
Much like nominate except crest. Dimorphic, with the dark morph chocolate-brown all over, tail base might appear lighter in flight.
Andaman Islands
Similar to N. c. limnaeetus. Apparently no dark morph.
Simeulue Island
Similar to N. c. limnaeetus. Apparently no dark morph.

Gamauf et al. (2005) analyzed mtDNA cytochrome b and control region sequence data of a considerable number of specimens of the crested hawk-eagle and some relatives. Despite the large sample, even the most conspicuous dichotomy - that between the crested and crestless groups - was not as well resolved as it might have been expected to be.

The three small-island taxa (N. c. andamanensis, N. c. vanheurni, and N. floris) also appear as monophyletic lineages. Their placement is even more unresolved, with N. floris being apparently a very ancient lineage. The other two seem quite certainly to derive from N. c. limnaeetus. The latter taxon has a confusing phylogeny. Different lineages exist that are apparently not stable in space and time, are best described as polytomy, from which the similar island taxa derive.

Obviously, N. c. limnaeetus does not represent a monophyletic lineage. Neither the biological nor the phylogenetic species concepts, nor phylogenetic systematics can be applied to satisfaction. It appears as if the crested group is close to becoming a distinct species. The island taxa derived from N. c. limnaeetus appear to have undergone founder effects, which has restricted their genetic diversity. In the continental population, genetic diversity is considerable, and the evolutionary pattern of the 2 studied genes did not agree, and neither did the origin of specimens show clear structures. N. c. limnaeetus thus is best considered a metapopulation.

Gamauf et al. (2005) therefore suggest that the island taxa which are obviously at higher risk of extinction are, for conservation considered evolutionary significant units regardless of their systematic status. This case also demonstrates that a too rigid interpretation of cladistics and the desire for monophyletic taxa, as well as universal application of single species concept to all birds will undermine correct understanding of evolutionary relationships. It would even not be inconceivable to find mainland lineages to group closely with the western island taxa, if little genetic drift had occurred in the initial population. nonetheless, the divergence of this species' lineages seems to have taken place too recently to award them species status, as compared to the level of genetic divergence at which clades are usually considered distinct species.

N. c. limnaeetus appears for all that can be said with reasonable certainty basal pool of lineages in the crestless group that, despite not being monophyletic, should be considered a valid taxon as long as gene flow is possible through its range. In addition, as ancient DNA from museum specimens was used extensively, the possibility of ghost lineages must be considered. If it is assumed that all or most of the ancient lineages still exist today, considerable recombination must have taken place as the two genes' phylogenies do not agree much, indicating a healthy level of gene flow. Whether this still holds true today remains to be determined.

Notes[edit]

  1. ^ BirdLife International (2013). "Nisaetus cirrhatus". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013. 
  2. ^ Helbig AJ, Kocum A, Seibold I & Braun MJ (2005) A multi-gene phylogeny of aquiline eagles (Aves: Accipitriformes) reveals extensive paraphyly at the genus level. Molecular phylogenetics and evolution 35(1):147-164 PDF
  3. ^ http://www.eagledirectory.org/species/crested_hawk_eagle.html
  4. ^ a b Ferguson-Lees & Christie (2001). Raptors of the World. Christopher Helm, London. ISBN 0713680261
  5. ^ Gjershaug, J. O., Kvaløy, K., Røv, N., Prawiradilaga, D. M., Suparman, U., and Rahman, Z. (2004). The taxonomic status of Flores Hawk-Eagle Spizaetus floris. Forktail 20: 55–62
  6. ^ Amadon, D. 1953. Remarks on the Asiatic Hawk-Eagles of the genus Spizaetus. Ibis 95:492–500.

References[edit]

  • Ali, Salim & Daniel, J.C. (1983): The book of Indian Birds (Twelfth Centenary edition). Bombay Natural History Society/Oxford University Press, New Delhi
  • Gamauf, Anita; Gjershaug, Jan-Ove; Røv, Nils; Kvaløy, Kirsti & Haring, Elisabeth (2005): Species or subspecies? The dilemma of taxonomic ranking of some South-East Asian hawk-eagles (genus Spizaetus). Bird Conservation International 15(1): 99–117. doi:10.1017/S0959270905000080 (HTML abstract)
  • Grimmett, Richard; Inskipp, Carol, Inskipp, Tim & Byers, Clive (1999): Birds of India, Pakistan, Nepal, Bangladesh, Bhutan, Sri Lanka, and the Maldives. Princeton University Press, Princeton, N.J.. ISBN 0-691-04910-6
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