the young may have an intermediate character; or again they may differ
greatly from the adults in both their seasonal plumages.
VI. In some few cases the young in their first plumage differ from each
other according to sex; the young males resembling more or less closely
the adult males, and the young females more or less closely the adult
females.
CLASS I. In this class, the young of both sexes more or less closely
resemble the adult female, whilst the adult male differs from the adult
female, often in the most conspicuous manner. Innumerable instances in
all Orders could be given; it will suffice to call to mind the common
pheasant, duck, and house-sparrow. The cases under this class graduate
into others. Thus the two sexes when adult may differ so slightly, and
the young so slightly from the adults, that it is doubtful whether such
cases ought to come under the present, or under the third or fourth
classes. So again the young of the two sexes, instead of being quite
alike, may differ in a slight degree from each other, as in our sixth
class. These transitional cases, however, are few, or at least are not
strongly pronounced, in comparison with those which come strictly under
the present class.
The force of the present law is well shewn in those groups, in which,
as a general rule, the two sexes and the young are all alike; for when
in these groups the male does differ from the female, as with certain
parrots, kingfishers, pigeons, etc., the young of both sexes resemble
the adult female. (2. See, for instance, Mr. Gould s account ( Handbook
to the Birds of Australia, vol. i. p. 133) of Cyanalcyon (one of the
Kingfishers), in which, however, the young male, though resembling the
adult female, is less brilliantly coloured. In some species of Dacelo
the males have blue tails, and the females brown ones; and Mr. R.B.
Sharpe informs me that the tail of the young male of D. gaudichaudi is
at first brown. Mr. Gould has described (ibid. vol. ii. pp. 14, 20, 37)
the sexes and the young of certain black Cockatoos and of the King
Lory, with which the same rule prevails. Also Jerdon ( Birds of India,
vol. i. p. 260) on the Palaeornis rosa, in which the young are more
like the female than the male. See Audubon ( Ornithological Biography,
vol. ii. p. 475) on the two sexes and the young of Columba passerina.)
We see the same fact exhibited still more clearly in certain anomalous
cases; thus the male of Heliothrix auriculata (one of the
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