Aquila mogilnik, S. S. Gm.
27. :- A. imperialis, Bechst.; Jerdon's Birds of India, Vol. I, p. 57 (in part) ; Butler, Deccan ; Stray Feathers, Vol. IX, p. 372 ; Aquila heliaca, Sav.; Murray's Vertebrate Zoology of Sind, p. 74; Hume's Scrap Book, p. 142.
THE IMPERIAL EAGLE.
Length, 28.5 to 30.5 ; expanse, 69 to 76; wing, 20.75 to 23; tail, 10.5 to 12.5 ; tarsus, 3.38 to 4; bill from gape, 2.13 to 2.63.
Length, 30 to 32.63 ; expanse, 70 to 85; wing, 23 to 24.5 ; tail, 12 to 14; tarsus, 3.75 to 4.06 ; bill from gape, 2.75 to 3.13.
Bill pale bluish-grey, bluish-horny at tip ; cere, gape and base of lower mandible deep yellow, tinged green near nostril; legs and feet dingy-yellow ; claws black.
This bird has two well marked stages of plumage : :- 1st. :- The general character of this stage is lineated. The under parts with broader or narrower pale centres to the feathers, and the upper parts with pale central stripes. What I take to be the earliest form of this stage has the head and nape brown, the feathers tipped and margined with pale yellowish-brown; the upper back, scapulars, and lesser wing-coverts darker brown, most of them showing faint traces of paler centres and tips, and some faintly margined slightly paler.
The lower back is buffy, a patch on the rump being mottled with brown, the upper tail-coverts being fulvous-white; the tail-feathers pale wood-brown, much abraded with dirty fulvous tips, and showing towards the bases traces of a mottled, paler, -and darker barring.
The primary quills are dark-brown, almost black; the secondaries and tertiaries paler and dingier brown, with a mere trace of a fulvous-white tipping, but the tertiaries are a good deal mottled with fulvous-white; the median and greater wing-coverts are, here and there, tipped with fulvous-white, but many are not so; the chin, throat, sides of the neck, breast, and abdomen are pale buffy-brown; the feathers margined with darker-brown, which latter, however, is very narrow, and almost wanting on most of the throat feathers, while it occupies the greater portion of the feathers on the lower breast and abdomen; the tibial plumes, vent, and lower tail-coverts are dingy reddish-buff; the lesser and median lower wing-coverts are reddish-buff, more or less centred with brown, and the greater lower wing-coverts are mingled white and blackish-brown; the lineation of the lower surface is more obscure and ill-defined than in what I take to be later forms of this same stage. In the next form of this stage every feather of the head, nape, and upper back is brown (a soft hair brown), darker than the form above described, with a conspicuous narrow, fulvous, central stripe. All the wing-coverts and scapulars are tipped with fulvous or fulvous-white, the lesser ones narrowly, in fact with a mere spot at the tip :- the larger ones more broadly; the rump, back and upper tail-coverts are as above described ; but the tail is a dingy wood-brown, without any trace of bars, and broadly tipped with fulvous-white.
The secondaries are conspicuously tipped with white or fulvous white; the chin, throat, and ear-coverts are unstreaked fulvous ; the breast and upper two-thirds of the abdomen are a warm,, somewhat purplish-brown, with conspicuous, well defined, narrow, central fulvous stripes; the lesser and median lower wing-coverts are more mingled with brown than in the specimen above described, and the larger lower-coverts are greyish-white, mottled with blackish-brown, and the axillaries, which, in the form first described, were reddish-buff, mottled with brown, are in this one similar to the feathers of the breast. In another form of this stage the head and back resemble the form first described; the tail and wings the second; while the chin, throat and ear-coverts are very pale buff, and the breast and abdomen are of the same color, each feather narrowly margined with the warm purplish-brown.
Specimens in this stage vary greatly, independently of the points noted above ; in the color of the thighs, vent and lower tail-coverts (which in some are nearly white, in others rufous buff), and in the extent and purity of the white, or fulvous-white tipping, to the tail and secondaries. The difficulty is, that these various differences do not go together. If the birds be arranged in a series, with reference to the comparative width of the central stripes of the breast feathers, which width varies, as above noticed, from less than one-fifth to nearly four-fifths of the total width of the feathers, and then turned back upwards, no corresponding progression in the lineation of the upper surface is observable, and, in order to obtain a regular series, according to the extent and amount of the lineations of the upper feathers, a totally different arrangement will be necessary. Adopting either of these arrangements, we shall still have no regular progression in the extent or purity of the white tipping of the tail, or secondaries, or in the color of the lower abdomen, vent, and leg-feathers.
Two birds, whose heads, necks, and upper backs correspond, differ entirely where the lower plumage, or perhaps tail-feathers, are concerned, and vice versa. It is clear, therefore, that some birds change first below, others above; some earlier on the heads and others on the tails; thus rendering the determination of the comparative priority of the various forms doubly difficult.
The adult stage is well-known. The whole head, nape, cheeks, ear-coverts, and sides of the neck, buff or orange-buff; the back, scapulars (except a few which are pure white), upper tail-coverts, wing-coverts, primaries, and secondaries, chin, throat, breast, abdomen, leg-feathers, sides, axillaries, and wing-lining, deep blackish-brown; the lesser wing-coverts margined, and the upper tail-coverts tipped with fulvous-white ; the lower tail-coverts white, and a good deal of white mottling about the tertiaries, which are a pale-brown; the tail grey, with a very broad terminal black band, occupying fully two-fifths of its visible surface, and above this, a number of more or less broad, irregular mottled, and imperfect transverse dark brown bands, which sometimes do, and sometimes do not, coincide exactly at the shaft.
This is what I take to be the perfect adult. In less advanced examples of this stage, the forehead, and more or less of the crown, are blackish-brown; the feathers of the chin and throat, as well as the upper breast, are margined, more or less broadly, with the same orange-buff as the head and nape.
The axillaries and lower wing-coverts are more or less mottled with rufous; the lower tail-coverts with rufous-brown; and the ground color of the tail, above the black tip, is pale yellowish-stone color rather than grey; the upper tail-coverts likewise are paler brown, and more broadly tipped with fulvous-white. In this stage, too, the changes are not synchronous; birds most advanced about the head being often least so about the tail; those most advanced on the upper, least so on the under surface, and vice versa.
The amount of white on the scapulars, too, varies greatly; some have only a single feather, others nearly the whole scapulars white, and I have some specimens, perfect adults, as regards the plumage on every other point, but exhibiting no trace whatsoever of white on the scapulars. :- Hume, " Rough Notes."
The Imperial Eagle is by no means common. It occurs throughout the region, excepting perhaps Guzerat.