SUMMER PLUMAGE. 
181 
L HiP. 
XV. 
The female is thus rendered 
to both sexes, 
a® conspicuous during the period of incubation than 
n S the winter ; but such birds as herons and egrets 
pi 1 be able to defend themselves. As, however, 
of lQes would probably be inconvenient and certainly 
] lft p 0 u se during the winter, it is possible that the 
°f moulting twice in the year may have been 
sui Uall y acquired through natural selection for the 
tyj ' 10 casting off inconvenient ornaments during the 
'h? er * ^*’ s Vlew canu °t be extended to the many 
>■ ers > in which the summer and winter plumages 
very little in colour. With defenceless species. 
%v 
either both sexes or the males alone become 
o r leni ely conspicuous during the breeding-season, — 
, ; ;^n the males acquire at this season such long 
n ® 0r tail-feathers as to impede their flight, as with 
^ , lQ 6 t° r uis and Vidua, — it certainly at first appears 
fojf 1 y Probable that the second moult has been gained 
flie special purpose of throwing off these ornaments. 
Pi^ust, however, remember that many birds, such as 
‘>ot 
\y le special purpose of throwing 
. uust, however, remember tha — , 
8 °f Paradise, the Argus pheasant and peacock, do 
W !l ^ lel ' r P^ umes during the winter ; and it can 
. * ,e maintained that there is something in the 
iwf ltut ion of these birds, at least of the Gallinaceae, 
'^Uerin... „ u : f at... • . ... 
Vts 
H 
er »ng a double moult impossible, for the ptarmigan 
ts thrice in the year . 31 Hence it must be eon- 
O* as doubtful whether the many species which 
1 1 their ornamental plumes or lose their bright 
^ during the winter, have acquired this habit on 
t^j ni,| t of the inconvenience or danger which they would 
j 6 l wis e have suffered. 
(; ° n elude, therefore, that the habit of moulting 
the year was in most or all cases first acquired 
31 See Gould’s ‘Birds of Great Britain.’ 
