character which is retained throughout life by many species, but is
quite lost by others, as by the Turdus migratorius. So again with many
thrushes, the feathers on the back are mottled before they are moulted
for the first time, and this character is retained for life by certain
eastern species. The young of many species of shrikes (Lanius), of some
woodpeckers, and of an Indian pigeon (Chalcophaps indicus), are
transversely striped on the under surface; and certain allied species
or whole genera are similarly marked when adult. In some closely-allied
and resplendent Indian cuckoos (Chrysococcyx), the mature species
differ considerably from one another in colour, but the young cannot be
distinguished. The young of an Indian goose (Sarkidiornis melanonotus)
closely resemble in plumage an allied genus, Dendrocygna, when mature.
(1. In regard to thrushes, shrikes, and woodpeckers, see Mr. Blyth, in
Charlesworth s Mag. of Nat. Hist. vol. i. 1837, p. 304; also footnote
to his translation of Cuvier s Regne Animal, p. 159. I give the case
of Loxia on Mr. Blyth s information. On thrushes, see also Audubon,
Ornith. Biog. vol. ii. p. 195. On Chrysococcyx and Chalcophaps,
Blyth, as quoted in Jerdon s Birds of India, vol. iii. p. 485. On
Sarkidiornis, Blyth, in Ibis, 1867, p. 175.) Similar facts will
hereafter be given in regard to certain herons. Young black-grouse
(Tetrao tetrix) resemble the young as well as the old of certain other
species, for instance the red-grouse or T. scoticus. Finally, as Mr.
Blyth, who has attended closely to this subject, has well remarked, the
natural affinities of many species are best exhibited in their immature
plumage; and as the true affinities of all organic beings depend on
their descent from a common progenitor, this remark strongly confirms
the belief that the immature plumage approximately shews us the former
or ancestral condition of the species.
Although many young birds, belonging to various families, thus give us
a glimpse of the plumage of their remote progenitors, yet there are
many other birds, both dull-coloured and bright-coloured, in which the
young closely resemble their parents. In such cases the young of the
different species cannot resemble each other more closely than do the
parents; nor can they strikingly resemble allied forms when adult. They
give us but little insight into the plumage of their progenitors,
excepting in so far that, when the young and the old are coloured in
the same general manner throughout a whole group of species, it is
probable that their progenitors were similarly coloured.
488