The cases in this class are singularly complex; nor is this surprising,
as they depend on inheritance, limited in a greater or less degree in
three different ways, namely, by sex, age, and the season of the year.
In some cases the individuals of the same species pass through at least
five distinct states of plumage. With the species, in which the male
differs from the female during the summer season alone, or, which is
rarer, during both seasons (41. For illustrative cases, see vol. iv. of
Macgillivray s History of British Birds; on Tringa, etc., pp. 229,
271; on the Machetes, p. 172; on the Charadrius hiaticula, p. 118; on
the Charadrius pluvialis, p. 94.), the young generally resemble the
females, as with the so-called goldfinch of North America, and
apparently with the splendid Maluri of Australia. (42. For the
goldfinch of N. America, Fringilla tristis, Linn., see Audubon,
Ornithological Biography, vol. i. p. 172. For the Maluri, Gould s
Handbook of the Birds of Australia, vol. i. p. 318.) With those
species, the sexes of which are alike during both the summer and
winter, the young may resemble the adults, firstly, in their winter
dress; secondly, and this is of much rarer occurrence, in their summer
dress; thirdly, they may be intermediate between these two states; and,
fourthly, they may differ greatly from the adults at all seasons. We
have an instance of the first of these four cases in one of the egrets
of India (Buphus coromandus), in which the young and the adults of both
sexes are white during the winter, the adults becoming golden-buff
during the summer.
With the gaper (Anastomus oscitans) of India we have a similar case,
but the colours are reversed: for the young and the adults of both
sexes are grey and black during the winter, the adults becoming white
during the summer. (43. I am indebted to Mr. Blyth for information as
to the Buphus; see also Jerdon, Birds of India, vol. iii. p. 749. On
the Anastomus, see Blyth, in Ibis, 1867, p. 173.) As an instance of
the second case, the young of the razor-bill (Alca torda, Linn.), in an
early state of plumage, are coloured like the adults during the summer;
and the young of the white-crowned sparrow of North America (Fringilla
leucophrys), as soon as fledged, have elegant white stripes on their
heads, which are lost by the young and the old during the winter. (44.
On the Alca, see Macgillivray, Hist. Brit. Birds, vol. v. p. 347. On
the Fringilla leucophrys, Audubon, ibid. vol. ii. p. 89. I shall have
hereafter to refer to the young of certain herons and egrets being
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