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.
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.
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. 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. The underparts and head of juveniles are whitish or buff with few dark streaks.
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. 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.
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).