NORTHERN THREE-TOED WOODPECKER. 45 
description with the detailed ones found in some works, 
we must conclude that the species is subject to variations 
in size and plumage, which, according to the erroneous 
impression given by authors, could not be satisfactorily 
accounted for by difference of sex, age, or locality: 
thus in some specimens the cervix is described white, 
or partly whitish, instead of being wholly black : the 
back is also said to be waved with while ; which is 
indeed the case, and with the cervix also, but only in 
young birds. There is a circumstance, however, that 
could not be explained by supposing a difference of age, 
for while some specimens are seen with no appearance 
of white or yellow on the crown, but having that part, 
as well as the body, rich shining black, others with a 
good deal of lemon yellow' on that part, are of a duller 
black, much varied with white. As in other doubtful 
and intricate cases, these obscurities are dissipated by 
a close inspection and unprejudiced observation of 
nature, and we feel much gratification in being enabled 
to unveil to ornithologists the mystery of these diversities 
of plumage in this species, by merely pointing out the 
sexual differences, as well as those originating in the 
gradual change from youth to maturity in both sexes ; 
which, when understood, will not be found more 
extraordinary than in other species. 
The adult female has never been recognized by any 
author, nor, hitherto, even by ourselves, having been 
misled by others in taking the young for her ; and this 
we have only discovered by inspecting a great many 
specimens. She is precisely similar to the male, even 
in the minutest particulars, excepting the absence of 
yellow on the head, this part being of a rich and glossy 
black. 
The young of both sexes are of a dull blackish ; the 
setaceous feathers of the nostrils are grayish, somewhat 
tinged with rusty; all the feathers of the crown are 
tipped with white, constituting thick dots on that part, 
to which they give a silvery appearance ; the cheek bands 
are obscure and much narrower ; the cervix is more or 
less varied with white, and the feathers of the back 
