The underside in this race has a paler ground colour against much browner and darker barring, often showing less of the warmer or rufous tones typical of mainland mountain hawk-eagles.

A 2008 study based on the geographic isolation and differences in call suggest that this be treated as a full species, Nisaetus kelaarti, Legge's hawk-eagle.

The malar area and throat are marked with blackish, ragged and sparse but rather bold stripes which contrast with the rest of their underside which is predominantly barred with rufous over a whitish ground colour.

The underside colour also extends to the head and part of the neck flanks while the crown, cheek, nape and hind-neck all streaked with dark brown.

[6] In flight, it is notable for its rather prominent head and relatively short rounded wings, an effect emphasized by their broad hands and bulging secondaries, which tend to pinch in at the rear bases.

The wing linings of adults are a rusty similar to flank coloring, becoming paler on forepart and marked with dusky mottling which becomes darker mid-wing.

Another, albeit unlikely, potential source of confusion for the mountain hawk-eagle is with Jerdon's baza (Aviceda jerdoni), which is far smaller, and of a far more compact and chunky build.

Mountain hawk-eagles can usually be told from the slighter, smaller crested honey buzzard (Pernis ptilorhynchus), beyond the latter being polymorphic, as even most similarly plumaged individual honey buzzards have bare legs, much smaller and slimmer head and bill with a longer neck and deeper wing beats on relatively longer, more slender wings.

[1][6][12] The mountain hawk-eagle is distributed through the Himalayas, extending from northeastern Pakistan through north India in at least the states of central Jammu and Kashmir, Himachal Pradesh and Uttarakhand, continuing into Nepal, Bhutan to northern Assam thence southward into the north and east Burmese highlands, west and peninsular Thailand, also the northern parts of Laos and probably Vietnam.

Their range continues eastward into southeastern China where they may be found in Yunnan, Guangxi and Guangdong Province northward in the east to the lower reaches of the Yangtze in Anhui and Zhejiang.

To this date, the IUCN has not updated the range maps for mountain hawk-eagles to reflect the species’ presence in these areas, although their status as continual breeders here may still need confirmation.

[47] With a fair amount of consistency, the hawk-eagles found in the northern part of southeast Asia range into more lowland areas of Burma, eastern Thailand and peninsular Malaysia.

In some of the areas above such as Thailand and Malaysia (mainly far northern part of country), year-around reports of mountain hawk-eagles may suggest small, isolated pockets of residency and/or breeding occurring.

In non-breeding times, mountain hawk-eagles may sometimes wander through wooded plains and briefly near fairly developed villages (though usually more secluded and primitive one) and even cities.

[6] Mountain hawk-eagles have also been observed catching passerines on the wing by giving chase from an ambush or when the prey is flushed by flying low at the canopy level.

How they capture these elusive and nocturnal rodents is not clear, but perhaps the flying squirrels’ relatively huge size makes them more conspicuous from the hawk-eagle's lofty perch.

Quantitatively, most prey deliveries by this pair were rather (almost surprisingly) small in body size, whether this is typical of Japanese hawk-eagles is not clear given the lack of comprehensive study.

The most often delivered prey (18.2% of her 44 deliveries) by the female once she resumed hunting were larger class Elaphe snakes, in excess of 100 cm (39 in) length and 325 g (11.5 oz).

[62][63] In Jim Corbett National Park, India, prey reportedly consisted largely of smallish or medium-sized birds (albeit probably larger than those in the above Japanese study) such as mynas, doves, parakeets, nightjars, owls and village poultry.

[12] In the Russian Far East, apparently the most important prey types were reported as Manchurian hares (Lepus mandshuricus), a close cousin and of the same size as the Japanese hare, and hazel grouse (Tetrastes bonasia), while most of the remainder of the diet consisted of a mixture of smallish mammals like (moles, hedgehogs and flying squirrels) and largish forest birds (woodpeckers, pheasants and owls).

[67] Larger avian prey has been taken by mountain hawk-eagles, including adult Indian peafowl (Pavo cristatus) weighing up to an estimated 4 kg (8.8 lb).

Meanwhile, four adult Chinese ferret-badgers (Melogale moschata), weighing on average about 1.3 kg (2.9 lb), were taken in Taiwan, while a Japanese marten (Martes melampus) of the same estimated weight was taken there by a female hawk-eagle.

[74][75][76][77] However, the most impressive primate kill was an adult Japanese macaque (Macaca fuscata), estimated to weigh somewhere between 8.3 and 10 kg (18 and 22 lb), that was taken alive and subsequently dismantled by a large (presumed female) mountain hawk-eagle.

Their aerial display includes conspicuous and often noisy high circling, both single and mutual, and undulating sky dance of steep dives and climbs with bubbling call uttered at each peak.

Many nests are often near a steep-edged ravine, or alternately near a natural tree line, freshwater wetland or other environment that provides ample view of the surrounding area.

The aggressiveness of the female may rival that of the often co-occurring spot-bellied eagle-owl and even outrival the defensive attacks on human by the more powerful African crowned eagle.

Even when struck with branches, machetes or fist and hit with buckshot by humans, apparently the female will still not cease her attack unless killed or grievously injured.

[12][91][92][93] In one case, a local woman in the Kumaon division of northern India fell victim to a "particularly savage" attack by a female mountain hawk-eagle and subsequently died from the injuries sustained.

In particular, the increasing density of human populations in northern India, southeastern China and Japan are likely to continue to facilitate declines in forest quantity and quality.

[1][6][13][102][103] As the species is a K-strategist like all eagles, it was feared that the ongoing population reduction of N. n. orientalis might lead to loss of genetic diversity, and consequently inbreeding depression.