From observations which have been made with great care and exactness, and which any one can repeat who wishes, it appears proved that an old male bird never changes its colour. In order to be exact as to these facts, it is necessary to observe the bird from the time of its leaving the nest; for, if one were to judge from those taken in a snare, one would certainly be disposed to think that not one bird resembled another: but all this variety depends on the different stages in moulting, which so very much affects the colours of the plumage. Thus, in old male birds the forehead, cheeks, and eyebrows are spotted with grey, greenish yellow, and white. Wherever green and yellow are prevalent, the dark grey shows through, and has the appearance of spots on those parts, particularly on the back, for the tips alone are green and yellow. The result of all this is, that when grey or speckled crossbills are spoken of, they are the young ones; when red, they have passed their first moulting; when crimson, they are near their second; and when spotted, red and yellow, they are two years old, and in full feather. To judge with exactness, these birds ought to be seen at the time of laying, but neither this nor the moulting has any fixed season; and this circumstance sufficiently explains the great variety and difference of colour which are found among this species. These details also show that the crossbill is subject to nearly the same changes of colour as the linnet, and that the red colour which it bears for the first year is what peculiarly distinguishes it from other birds. One thing, which is rather remarkable, is, that the young ones reared in the house never take the red colour, but remain grey for the second year, or change directly into greenish yellow. There are two kinds of crossbills, the greater and lesser; but the difference is not so great as some pretend, and nature is not more invariable in the size of birds than it is in that of men[29]. HABITATION.--When wild, the crossbill not only inhabits Europe, but also all the north of Asia and America, everywhere frequenting forests of pines and firs, where these trees, which are loaded with cones, furnish abundance of food. In the house it may be let range at will, but a branch of fir, or any other tree, must be put near it, on which it can perch or sleep. If it be kept in a cage it must be made of wire; for, being so much disposed to peck and nibble, a wicker cage would soon be reduced to chips. FOOD.--In its wild state the pine seed is its favourite food; the shape of its beak is peculiarly adapted for procuring these seeds, by separating the scales of the cones; it also gathers from the ground those which have fallen, and it does not neglect those of the fir, and even of the alder. When these fail it is contented with the buds of the same trees.