drongos (Bhringa) in India, and with the elongated feathers on the
back, neck, and crest of certain herons. By such steps as these, the
vernal moult might be rendered more and more complete, until a perfect
double moult was acquired. Some of the birds of paradise retain their
nuptial feathers throughout the year, and thus have only a single
moult; others cast them directly after the breeding-season, and thus
have a double moult; and others again cast them at this season during
the first year, but not afterwards; so that these latter species are
intermediate in their manner of moulting. There is also a great
difference with many birds in the length of time during which the two
annual plumages are retained; so that the one might come to be retained
for the whole year, and the other completely lost. Thus in the spring
Machetes pugnax retains his ruff for barely two months. In Natal the
male widow-bird (Chera progne) acquires his fine plumage and long
tail-feathers in December or January, and loses them in March; so that
they are retained only for about three months. Most species, which
undergo a double moult, keep their ornamental feathers for about six
months. The male, however, of the wild Gallus bankiva retains his
neck-hackles for nine or ten months; and when these are cast off, the
underlying black feathers on the neck are fully exposed to view. But
with the domesticated descendant of this species, the neck-hackles of
the male are immediately replaced by new ones; so that we here see, as
to part of the plumage, a double moult changed under domestication into
a single moult. (82. For the foregoing statements in regard to partial
moults, and on old males retaining their nuptial plumage, see Jerdon,
on bustards and plovers, in Birds of India, vol. iii. pp. 617, 637,
709, 711. Also Blyth in Land and Water, 1867, p. 84. On the moulting
of Paradisea, see an interesting article by Dr. W. Marshall, Archives
Neerlandaises, tom. vi. 1871. On the Vidua, Ibis, vol. iii. 1861, p.
133. On the Drongo-shrikes, Jerdon, ibid. vol. i. p. 435. On the vernal
moult of the Herodias bubulcus, Mr. S.S. Allen, in Ibis, 1863, p. 33.
On Gallus bankiva, Blyth, in Annals and Mag. of Natural History, vol.
i. 1848, p. 455; see, also, on this subject, my Variation of Animals
under Domestication, vol. i. p. 236.)
The common drake (Anas boschas), after the breeding-season, is well
known to lose his male plumage for a period of three months, during
which time he assumes that of the female. The male pin-tail duck (Anas
acuta) loses his plumage for the shorter period of six weeks or two
months; and Montagu remarks that this double moult within so short a
415