52 
STRIGII)^>. 
markings are very little if at all influenced by sex. I believe 
that the adult female also becomes white, and have seen one 
very nearly in that state. Full growth is attained about the 
end of the first winter, after which time size is a trustworthy 
indication of sex, the male seldom exceeding twenty- three 
inches in length, while twenty-six inches is the usual length 
of a female. The younger the bird the more do the dark 
marks^ especially on the under surface of the body, partake of 
a barred appearance ; the sharper are the edges and tips of the 
mandibles ; and the broader and thinner, although no less 
keen, is the projecting inner edge of the middle claw. All of 
the claws are comparatively slender, and in colour resemble the 
bill, being of a bluish or greyish tinge, while in the adult those 
parts are black. Intensity of colouring has often been regarded 
as a mere indication of advanced age, but this taken by itself is 
no criterion, for at most times there is a considerable variety 
of tint, even in the same individual, and very dark brown or 
black is nearly always present from the end of the first winter 
until some years afterwards. The truth seems to be, that in 
old birds the dark tints merely predominate, and for this 
reason, that as a general rule the lighter ones are the first to 
disappear.'* And yet this is not invariably the case, for speci- 
mens have been obtained which were perfectly white, with the 
exception of a few faint bars upon the wings or tail. Upon 
the body spots are usually darker than bars, and thus it is 
evident that the greater the abundance of bars upon the body^ 
the younger is the bird. The size of the spots probably de- 
creases with age, and is said to be larger in females than in 
males, but of this I have never yet been able to satisfy myself. 
The parts on which the marks show the greatest inclination to 
linger are the occiput, scapulars, wing coverts, tertials, and, 
more than all, upon the tail. Although an immature speci- 
men may appear to have the ground colour, so to speak, of the 
plumage perfectly white, comparison with an adult will at once 
show that it differs in several respects. The plumage of the 
* [Not a very clear jiassage. It seems hotter to transcribe vcrhntim. — Ed,] 
