Changeable Hawk-Eagle/ Crested Hawk-Eagle
Nisaetus cirrhatus cirrhatus
Yenkathala Grasslands, Tadoba Andhari Tiger Reserve, Kabini & Tipeshwar Wildlife Sanctuary
Continuing the story on the tropical raptors, like the Crested Serpent Eagle last week, this blog is about the Changeable Hawk-Eagle or Crested Hawk-Eagle (Nisaetus cirrhatus). The Changeable Hawk Eagle is a large bird of prey species of the family Accipitridae. More informal or antiquated English common names include the marsh hawk-eagle or Indian crested hawk-eagle.
Some of the Accipitridae I have already talked about earlier are the Harriers from Kumbhargaon -
The Changeable Hawk-Eagle is a member of the subfamily Aquilinae, with signature feathers, absent in tropical raptors from outside this subfamily, covering the tarsus. 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.
Some other Aquilinae are the -
The Changeable Hawk-Eagle is a typical “hawk-eagle” in that it is an agile forest-dwelling predator and like many such eagles readily varies its prey selection between birds, mammals or reptiles as well as other vertebrates. Among the members of its genus, the changeable hawk-eagle stands out as the most widely distributed, adaptable and abundant species. Birds show a wide range of variation in plumage from pale to dark, varying with moult and age giving rise to the name "changeable". With that said let’s spend a few minutes on the habitats I have seen these magnificent birds in - the central Indian forests of Tadoba & the lush Nilgiri Biosphere of Kabini.
Tadoba
Tadoba is a jungle where, early in the day, the sun follows one like a lodestar through the tangled heads of the trees and as the day progresses it burns with a blinding exquisiteness that makes us shield our eyes and bless our existence. The light is lustrous in the open spaces and seemed undistllled from heaven to earth seeming like a laser show at times as gem clear beams filter through the trees. The warmth of it settles over our faces like a silken mask and life is a golden joy. That is the thing about the seraph-light of this jungle; it can sweep down like the handloom of the gods one moment, pure and clear and long of line.
Tadoba lies in the Chandrapur district of Maharashtra state, once ruled by the Gond Kings in the vicinity of the Chimur Hills, and is approximately 150 km from the closest major city, Nagpur. The total area of the tiger reserve is 1,727 km², which includes the Tadoba National Park, created in the year 1955. The Andhari Wildlife Sanctuary was formed in the year 1986 and was amalgamated with the park in 1995 to establish the present Tadoba Andhari Tiger Reserve. The word 'Tadoba' is derived from the name of God "Tadoba" or "Taru," venerated by the local adivasi (tribal) people of this region and "Andhari" is derived from the name of the river Andhari flowing in this area. Legend holds that Taru was a village chief killed in a mythological encounter with a tiger. Taru was deified and a shrine now exists beneath a large tree on the banks of the Tadoba Lake. The temple is frequented by the adivasis between the months of December through January.
Tadoba is divided into three separate ranges - the Tadoba north range, Kolsa south range and the Moharli range sandwiched between the two. There are two lakes - Tadoba and Kolsa - and a river which are replenished by the monsoon every year sustaining the wildlife in the park. Rich in flora and fauna the vegetation is southern tropical dry deciduous and covers about 630 sq.km. Teak and bamboo are prominent and the northern and western parts of the reserve are hilly and dense with deep valleys and a sprinkling of lush meadows. Home to some of central India’s best native woodland bird species, about 181 including endangered and water birds, the park also boasts leopards, sloth bear, the Indian bison (Gaur), Nilgai, Dhole, Striped Hyena, small Indian Civet, numerous Jungle Cats, Chital (Axis Deer), Sambhar, Barking Deer, Four-horned antelope, Marsh Crocodiles, a profusion of Langurs and Rhesus Macaques and a good measure of reptiles like the Indian Python, Cobra and numerous other species. Tadoba, unfortunately, also has a high rate of man tiger conflict. Several instances have also been reported of wildlife killing domestic livestock and there are villages still within the forest contrary to the efforts of the Forest department so we were told. Note it is man conflicting with nature and not the other way round.
Kabini
In the lush Nilgiri Biosphere, to the south of the famed Nagarhole Tiger Reserve & National Park, on the banks of the river Kasbani lies the area known as Kabini. A major tributary of the Cauvery, the Kasbani is also known as the Kapila river and Kabini River giving the area its name. Consisting mainly of moist deciduous forests, interspersed with teak and eucalyptus plantations, and at a lower altitude compared to Bandipur across the river, Kabini is sprinkled with open grasslands, making it easy to spot wildlife, and providing amazing photographic opportunities.
The erstwhile exclusive hunting grounds of the kings of Mysore, Kabini has lush forests, small rivulets, hills, valleys and waterfalls making it a veritable paradise for many species like the tiger, dhole, gaur, elephants, chital, sambhar and the leopard. One can also spot the critically endangered oriental white-backed vulture, various species of eagles and the Nilgiri wood pigeon.
So that was about the habitat I have seen this magnificent bird of prey in. Now onto the bird itself.
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Read about my tigers from Central and South India
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Changeable Hawk-Eagle
The changeable hawk-eagle or crested hawk-eagle (Nisaetus cirrhatus) is a large bird of prey species of the family Accipitridae. It is a member of the subfamily Aquilinae, with signature feathers, absent in tropical raptors from outside this subfamily, covering the tarsus. 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. It is a typical “hawk-eagle” in that it is an agile forest-dwelling predator and like many such eagles readily varies its prey selection between birds, mammals or reptiles as well as other vertebrates. Among the members of its genus, the changeable hawk-eagle stands out as the most widely distributed, adaptable and abundant species. Birds show a wide range of variation in plumage from pale to dark, varying with moult and age giving rise to the name "changeable".
The taxonomy of the wide-ranging changeable hawk-eagle is complex and confusing, with few authorities agreeing on whether the species in fact houses a species complex. Two distinct groups exist in the changeable hawk-eagle; one with crests and one without or with hardly visible crests and dark morphs exist for some populations.
Sub-species:
Changeable hawk-eagle
N. c. cirrhatus: The nominate subspecies is found in the peninsular India, from the Gangetic plain southwards throughout the remainder of the country. It is monomorphic in colour with no dark morph. The nominate subspecies is relatively pale above compared to other races, with a slightly more rufous hue to the head. It tends to be less extensively streaked below down to the lower breast below compared to other races, with dark wing lings and a strongly barred tail.
N. c. ceylanensis: This race is endemic to Sri Lanka but some authorities also include Travancore in the southern tip of India as part of this race's range. This race has a proportionally longer crest on average than the nominate race, with a similar crest length to it at about 10 cm (3.9 in).
Crestless changeable hawk-eagle
N. c. limnaeetus: This race is found through the Himalayan foothills from Nepal, northeast India, via Burma to much of southeast Asia including the Malay Peninsula along Wallace Line to Philippines and the Greater Sunda Islands. This race can appear similar in size and build to the nominate race but unlike it is rather polymorphic and this is the most widely found of subspecies.
N. c. andamanensis: This race is found in the Andaman Islands. The subspecies is darker than the nominate subspecies and more similar to N. c. limnaeetus in hue but does not appear to have a full dark morph as is known in that race.
N. c. vanheurni: This race is native to Simeulue Island. It is similar in appearance to N. c. limnaeetus, but apparently lacks a dark morph. The subspecies is also much less heavily blotched black on its whiter looking breast and never bears a crest. It is the smallest accepted subspecies of the changeable hawk-eagle, considerably smaller than N. c. limnaeetus.
The changeable hawk-eagle is a largish but slender eagle. They fall near the middle of sizes among the currently accepted species in the genus Nisaetus. As in most birds of prey, females are larger than males with an average overall size difference of 7% but this can individually range to an 18-22% difference, with island races apparently thought to be less dimorphic on average. Size is quite variable and total length has been reported in the past to vary from 51 to 82 cm (20 to 32 in) and wingspan from 100 to 160 cm (39 to 63 in), however these figures appear to include the much more massive hawk-eagles from Flores that are currently considered their own separate species by modern authorities.
Adult changeable hawk-eagles are typically dark brown above and boldly streaked below with a strong bill, a variably sized, often floppy crest or no crest, rather short wings, a quite long, thinly-barred tail and long feathered legs. This species tends to perch “bolt” upright, and may perch in various places from somewhat secluded spots to also quite open area as well. They tend to have an evenly black-streaked and somewhat rufous-tinged head and neck, with a blackish crest (if present). The tail tends to be paler brown than the back with a thin whitish tip, a broad, blackish subterminal band (both the whitish tip and the subterminal band are also visible from tail underside) and 3 to 4 narrower, brown and often rather obscure bars. On the pale morph hawk-eagle's underside, the base colour is white to buff overlaid with bold black to dark brown streaking; the streaking tends to be more subtle on abdomen but more obvious on the legs.
The extensive range of the changeable hawk-eagle includes much of the Indian subcontinent and southeast Asia. Their distribution includes nations and areas such as Sri Lanka, Himalayan foothills (Garhwal to Assam), southern Nepal and Bhutan east through Myanmar, Burma, western Laos, southern Vietnam, Cambodia, Thailand and peninsular Malaysia. In India, they may found almost continuously from the peninsular tip north to Rajasthan, Uttar Pradesh, Bihar and Odisha. Its island distribution includes the Andamans, Sumatra (including Simeulue & Mentawai off the west side and Riau, Bangka and Belitung off of the east), Java, Borneo and the western and southern Philippines (including Palawan, Calamians, Lubang, Mindoro, Mindanao and apparently recently Bohol). Like most tropical raptors, the changeable hawk-eagle is largely residential, but stragglers from peninsular India have roamed to northeastern Burma and southeastern Thailand and some records in the Lesser Sunda Islands (Bali, Palau and Lombok) may be from vagrants from Java. The species may live in savannah woodland, cultivation with trees, timbered watercourses, tea plantations, forest villages and even suburban edge. Beyond these often degraded haunts they range as well as any of the more forest-clinging Nisaetus into fairly open or less dense parts of undisturbed vast evergreen (including tropical rainforest) or deciduous forests (their deciduous ranges mainly occurring in India and the Sunda islands), but also second growth and wetlands. In elevation, they may be found anywhere from sea level to 2,200 m (7,200 ft) but mainly live below 1,500 m (4,900 ft). It is not uncommon in foothills of Sri Lanka but again does not usually exceed 1,500 m (4,900 ft) elevation there.
Changeable hawk-eagles are at home in a variety of wooded and semi-open habitats. Their physical form and flight style is typical of forest-dwelling raptors in general and is often compared to the features of true hawks or Accipiters in particular larger species such as goshawks. Like most other forest raptors, changeable hawk-eagles (and Nisaetus species in general) have a long tail, short broad wings and relatively long but powerful legs, all of which impart greater manoeuvrability and quicker strike times in denser wooded hunting grounds than other raptorial body plans.
The habitat selection and overall distribution of the changeable hawk-eagle is largely concurrent with other largish raptors such as the crested serpent eagle and the crested honey buzzard, apparently the three species are largely tolerant and non-aggressive towards each other, perhaps surprisingly given the otherwise aggressive habits of hawk-eagles. Unsurprisingly, these species have quite discrepant ecological niches, especially in terms of their dietary habits.
The changeable hawk-eagle apparently ranges over 13 million square kilometers across its range. An average of only 1 pair to every 1,200 km (750 mi) of its distribution would put the population well into five figures but their density is likely rather higher. This species is an exceptionally adaptable one not only by the standards of its genus but also by the standards of its subfamily. While deforestation has depleted the populations of their fellow Nisaetus species, resulting in four being classified as Endangered species, the changeable hawk-eagle has been shown to be remarkably resilient in the face of cutting and habitat degradation. This trend, holding steady in population or even increasing while other hawk-eagle species have declined, has been reported in the Indian subcontinent, Malaysia, Java and the Philippines as well as elsewhere in southeast Asia.
With that said let’s move on to the gallery of this beautiful tropical raptor.
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