136 
DIVER. 
maturely feathered till the return of the breeding- season, many not 
till the second, or perhaps the third year. There is very little doubt 
the winter mew is no other than the young of the common gull ; as 
no doubt the wagel of authors is the young of the cobb of this 
work. It has been observed by an author of great ability, and for 
whom we have the highest respect, that the quill and tail feathers are 
permanent ; but in this we cannot agree, as we could produce innumer- 
able instances to the contrary. For instance : the male kestrel, which, 
from being barred on the tail feathers, becomes wholly ash-coloured, 
except at the end ; also the laughing gull, whose tail is at first 
tipped with black, and the quills without white at their ends, change 
in the first moulting. The herring-gull and others whose tail is 
white when matured, are for the first two years mottled. Besides 
the markings of the feathers, there are other markings which change 
by age and season, such as the colour of the bill, legs, irides, and skin, 
particularly the orbits of the eye. Some species of birds seem to 
change their winter and summer feathers, or at least in part : in some 
this is performed by moulting twice a year, as in the ptarmigan ; in 
others only additional feathers are thrown out. But we have no con- 
ception of the feathers themselves changing colour, although we have 
been informed of such happening in the course of one night. That 
confined birds do sometimes become wholly black, is unquestionable ; 
but this is occasioned by a succession of feathers ; and we have more than 
once seen the bullfinch in the state of changing, in which the black on 
the breast first appeared. The colouring of feathers is perhaps one of 
the most wonderful productions of nature. How the colouring secre- 
tions are disposed in such regular order, far surpasses human abilities 
to determine. It is probable, however, this is performed in an embryo 
state. The circulation in a feather seems to stop as fast as the parts 
are matured, and when it is fully grown, there certainly is no circu- 
latory fluid whatever ; of course the colours cannot change except in 
brilliancy. It might naturally be supposed for want of some secretory 
matter the feathers might become more brittle, or be injured, by wet or 
otherwise : but Nature, ever provident in all her ways, has taken care 
to supply every bird, more or less, with an external secretion of an 
unctuous nature, situated in a glandular bag upon the rump, which they 
instinctively make use of for oiling and dressing their feathers, as occa- 
sion requires. In water-fowl this bag is most conspicuous ; and it is 
remarkable that birds most frequently use it after washing, previous to 
their feathers becoming perfectly dry. 
DIVER {Colymhus^ Linn^us.)— -A genus of birds. 
