190 
sexual selection: birds. 
p art * 
remarkable facts recorded by Mr. Blytli , 5 with resp e f 
to closely-allied species which represent each othe* 11 
distinct countries. For with several of these repi' e8e 
tative species the adult males have undergone a 
ct? r ' 
tain amount of change and can be distinguished > 
ith 
females and the young being uudistinguishable, 
therefore absolutely unchanged. This is the case " -l _ 
certain Indian chats (Thamnobia), with certain how 1 ' 
suckers (Ncctarinia), shrikes (Tephrodornis), cert:l |, 
kingfishers (Tanysiptera), Ivallij pheasants (Gallop 1 ' 1 ' 
sis), and tree-partridges (Arboricola). . 
In some analogous cases, namely with birds ha v 'J’® 
a distinct summer and winter plumage, but with ( _ 
two sexes nearly alike, certain closely-allied spe°fj 
can easily be distinguished in their summer or n®P^. 
plumage, yet arc uudistinguishable in their winter 
well as in their immature plumage. This is the cl '\ 
with some of the closely-allied Indian wag-tails or ^ 
cilho. Mr. Swinhoe 6 informs me that three specie 3 '^, 
Ardeola, a genus of herons, which represent each ot ' » 
.rent 
hardly, if at all, distinguishable during the winter. ^[ e 
young also of these three species in their f 
plumage closely resemble the adults in their ' villt '.,, 
dress. This case is all the more interesting h ecal ! jl( 
with two other species of Ardeola both sexes i' e ^, 
during the winter and summer, nearly the same ph 1 
a-, (f 
5 See llis admirable paper in the < Jouri al of the Asiatic i. 
Bengal,’ vol. xix. 1850, p. 223; see also Jordon, ‘Birds of India,' ' ^1 
introduction, p. xxix. In regard to Tanysiptera, ITof. Schlcg® 1 ,, 
Mr. Blytli that ho could distinguish several distinct races, 
comparing the adult males. j oll s 
0 See also Mr. Swinhoe, in ‘Ibis,’ July, 1883, p. 131 ; and a P re b,;I 
paper, with an extract from a note by Mr. Blytli, in ‘Ibis,’ J° D ' 
p. 52. 
ou separate continents, arc “ most strikingly diffci -e 
when ornamented with their summer plumes, 
