158 
AVES. 
the accessory plume is large, but of soft and downy texture ; others have it reduced to ; 
a small tuft of down ; while in many it is absent altogether. In some Birds, the^ 
vanes of the feathers are to a variable extent united, or soldered into an uniform mass , 
and there are various additional modifications, too numerous to admit of detail]. The A 
touch must be feeble in all parts that are covered with them ; and, as the beak is 
almost always corneous and but little sensitive, and the toes are invested with scales - 
above and a callous skin underneath, this sense can be of little efficacy in the class of I 
Birds. [In the Snipes and Lamellirostres , however, the sense of touch in the bill must | 
be delicate, as testified by their manner of feeding, as weU as by the many nervous 
papillae distributed over its surface. The enarmous bill of the Toucans, also, is r. 
very sensitive ; and even the hardest biUs are traversed by ramifications of the fifth 
pair of nerves, which terminate in scattered papillae.] % 
The feathers are cast twice in the year [in some instances, but by far the greater ' 
number of Birds renew their plumage in autumn only ; and in no instance are the ' 
wing-primaries shed excepting in autumn, or at that moult which corresponds to the ; 
autumnal moult. Many, as the Hawks, larger Gulls, &c., retain their entire nestling! 
garb till the second autumn; while others, as the Crows, Starlings, &c., renew every ! 
feather previous to the first winter; and there are some groups, as that of the | 
Thrushes, together with various double-moulting Birds, as the Pipits and Wagtails, | 
which change their first clothing plumage soon after quitting the nest, but retain their ' 
nestling primaries until the second autumn — (that is, until the third renovation of the 
body feathers). In the Cormorants, Grebes, &c., some additional ornamental plumes are ^ 
developed towards the commencement of the breeding season ; at which time various i 
other Birds undergo a change of colour, unaccompanied by any moult * ; while others, f 
again, cast the terminal portion (commonly of a dingy hue) of the greater number of | 
their feathers, which during winter had concealed the brighter tints of summer ; two | 
or more of these various modes, by which a seasonal alteration of appearance is effected, | 
being frequently simultaneously observable in the same individual.] In certain species, | 
the winter plumage differs in its colours from that of summer ; and in the greater | 
number, the female differs from the male by colours less vivid, and the young of both ? 
sexes then resemble the female. When the adult male and female are of the same 
colour, the young have a peculiar livery. [As thus expressed, however, these rules f 
require to be qualified by numerous exceptions : the true enunciation of them being, 
that, when the plumage of the young differs from that of the adult male, or of the | 
female in those few cases where (as in the common Gallinule) this sex is the brighter, f 
that of the other sex may be similar to either of those extremes, or is in various 
decrees intermediate : the male and female of the common British Redstart, for 
O / 
instance, are dissimilar, and the young do not resemble the adult female ; but the'1 
garb of the latter is intermediate to those of the adult male and young.f] 
* When this takes place, as in certain Gambets {Totanus), the 
colouring matter is often entirely absorbed previously to the autumnal 
change of feather ; and in some double-moulting species, as the Golden 
Plover, it commonly happens in spring that the colouring secretion 
tinges the old feathers that are loose, and ready to drop off thus 
proving that a circulation obtains in the pores of feathers, even up to 
the period of their being naturally cast.— Ed. 
t There is a typical state of plumage in most groups of Birds,which, 
in certain species, as the Tree Sparrow, is common to old and young 
of both sexes ; but which is very usually obtained only by the adult 
male, as is observable in the common House Sparrow : in the Robin, 
Goldfinch, &c., to select other familiar examples, it is acquired by the 
adults of both sexes; and, in the Common Gallinule, only by the 
mature female. There are also many Birds in which neither sex 
assumes this comparatively advanced livery; the larger Bitterns, for 
example, both sexes of which permanently retain the markings and 
style of colouring characteristic of only the first or immature dress of 
the Dwarf-bitterns (subgenus Ardeola); the adult male common 
Bunting {Emberiza miliaria), also, thus exhibits correspond- 
ing livery to that proper to the females and young of the rest of its* 
group, never advancing, like the males of the other species of Bunting, 
beyond its primitive nestling colours and markings. We are led to 
recognize, therefore, two extreme conditions of plumage as regards 
the colouring, — one generally, but not always, characteristic of matu- 
