Nothing is known respecting their propagation in the United States, and as I have no desire to compile, I must pass over this subject. They leave us in the beginning of March, and betake themselves to more northern countries; yet not one did either myself, or my youthful and enterprising party, observe on my late rambles in Labrador.
I have given you the figure of what I suppose to have been a middle-aged bird, and will at another time place before you one of the dark-coloured kind, known by the name of Falco niger, but which I consider as the old bird of the present species.
However highly I esteem the labours of Wilson, I am here compelled to differ from him. How that accurate observer made two different species of the young and the adult Rough-legged Falcon, I cannot well understand, more especially as his description of Falco lagopus and F. niger are so similar, that one might infer from their comparison that they referred to the same species.
Of Falco lagopus he says:—"The Rough-legged Hawk measures twenty-two inches in length, and four feet two inches in extent; cere, sides of the mouth, and feet, rich yellow; legs feathered to the toes, with brownish-yellow plumage, streaked with brown; femorals the same; toes comparatively short; claws and bill blue-black; iris of the eye bright amber; upper part of the head pale ochre, streaked with brown; back and wings chocolate, each feather edged with bright ferruginous; first four primaries nearly black about the tips, edged externally with silvery in some lights; rest of the quills dark chocolate; lower, side, and interior vanes white; tail-coverts white; tail rounded, white, with a broad band of dark brown near the end, and tipt with white; body below, and breast, light yellow ochre, blotched and streaked with chocolate. What constitutes a characteristic mark of this bird, is a belt or girdle of very dark brown, passing round the belly just below the breast, and reaching under the wings to the rump; head very broad, and bill uncommonly small, suited to the humility of its prey.
"The female is much darker both above and below, particularly in the belt or girdle, which is nearly black; the tail-coverts are also spotted with chocolate; she is also something larger.
"The Black Hawk is twenty-one inches long, and four feet two inches in extent; bill bluish-black; cere and sides of the mouth orange-yellow; feet the same; eye very large; iris bright hazel; cartilage overhanging the eye prominently, of a dull greenish colour; general colour above brown-black, slightly dashed with dirty white; nape of the neck pure white under the surface; front white; whole lower parts black, with slight tinges of brown; and a few circular touches of the same on the femorals; legs feathered to the toes, and black, touched with brownish; the wings reach rather beyond the tip of the tail; the five first primaries are white on their inner vanes; tail rounded at the end, deep black, crossed with five narrow bands of pure white, and broadly tipped with dull white; vent black, spotted with white; inside vanes of the primaries snowy; claws black, strong, and sharp; toes remarkably short."
I have frequently examined the very specimen from which Wilson took his figure of the Falco niger, and which is now in the collection of the Academy of Natural Sciences at Philadelphia. On comparing it with specimens of the Rough-legged Falcon in its ordinary states, I could discover no essential differences, nor, in fact, any excepting such as have reference to colour, a circumstance or quality which in hawks is known to vary so much in almost every species at different periods of their lives, that it would be useless for me to offer any remarks on the subject. Besides this, Wilson's figure is by no means correct as to colouring, it being in fact black, in contradiction to his description. I have beside me specimens in which the colour of the plumage is very different, some being quite light, others almost black; and I feel pretty confident that further researches respecting this species will shew that my opinion is not incorrect, when I say that the Rough-legged Falcon of America and the Falco niger of Wilson, are the same bird.
I am of opinion that the reason for which the dark coloured individuals are of much rarer occurrence with us, than the lighter ones, is, that the former being older and stronger birds, are much better able to bear the inclemency of the weather in more northern regions.
Falco lagopus, Gmel. Syst. Nat. vol. i. p. 260.—Lath. Ind. Ornith. vol. i. p. 19.—Ch. Bonaparte, Synops. of Birds of the United States, p. 32.
Buteo lagopus, Swains. and Richards. Fauna Bor.-Amer. part ii. p. 52.