change is usually produced by the assumption of an entirely new tint, and very seldom by the spreading of any colour which belonged to the individual in its natural state. Still less frequently does it happen that the head, or any particular part of a bird, undergoes an accidental change, leaving the remaining parts in their natural plumage. Thus we occasionally find the starling, the blackbird, the sparrow, and several of the other finches, in a wild state, entirely changed to a white or cream colour, of which little or none belonged to the bird in its natural state. But instances do not occur in which the blue bars have spread over the whole wing of the jay; nor do we find that the whole head of the gold-crest ever assumes the bright yellow colour from which the bird derives its name. Although marks and spots vary in the depth of their tints, becoming in some species darker, in others brighter, according to the age of the bird, yet Nature seldom permits them to vary in size. She "has set them their bounds which they cannot pass." But to return to the capped buzzard. The specimen figured appears to be in the perfect barred plumage, which, as I have already hinted, there seems some reason to suppose to be attained simultaneously with the ash-coloured head. The bird described and drawn by Bewick, is in nearly the same plumage as this bird, and he says that " the head is large, flat, and ash-coloured."
Buffon says too that the head is large, flat, and of a grey cinereous; but he does not describe the rest of the bird. Some of your correspondents who may have met with specimens of the capped buzzard, can perhaps inform us if they correspond in other respects with this. If so, a question arises as to the age of the bird in this state of plumage—and whether the grey head is common to both sexes? The example in my possession (fig. 3) I must confess shows no signs of it. The head has a mottled appearance, the feathers being tipped with light brown; but in this bird the barred plumage has not attained perfection. Another foreign specimen in my possession, which was said to be a female, although in other respects almost exactly resembling fig. 4, has not the grey head. The tail is also somewhat differently marked, being very similar to that of the bird in the British Museum figured by Mr. Yarrell.
A link is here wanting to show more clearly the change from the barred plumage of the breast and under parts to the pure white. The bird, however, from which
Figure 5
was drawn, has some patches of brown on the breast, which appear to indicate the former existence of those bars. The forehead is white;
