8 2 SEXUAL SELECTION: BIRDS. PAR? 11 ' 
direct action of the conditions of life. But with mo 11 ) 
birds there can hardly be a doubt that the sumn 1 ^ 
plumage is ornamental, even when both sexes are ali^ e ' 
We may conclude that this is the case with man)* 
herons, egrets, &c., for they acquire their beautii ' 1 
plumes only during the breeding-season. Moreover 
such plumes, top-knots, &c., though possessed by bod 1 
sexes, are occasionally a little more highly developed 111 
the male than in the female; and they resemble d 1? 
plumes and ornaments possessed by the males al°” f 
of other birds. It is also known that confinement, W 
affecting the reproductive system of male birds, h f * 
quently checks the development of their second^') 
sexual characters, but has no immediate influence 
any other characters ; and I am informed by ^ r ‘ 
Bartlett that eight or nine specimens of the Kd° 
(: Tringa canutus) retained their unadorned winter 
mage in the Zoological Gardens throughout the ye‘‘ ir ' 
from which fact we may infer that the summer pluina?' 
though common to both sexes partakes of the nat» re 
of the exclusively masculine plumage of many otF ’ 1 
birds . 75 
From the foregoing facts, more especially fr 01 ’ 1 
neither sex of certain birds changing colour duri"' 
either annual moult, or changing so slightly that tb 
change can hardly be of any service to them, and 
the females of other species moulting twice yet rota' 1 ' 
ing the same colours throughout the year, we may C °K 
elude that the habit of moulting twice in the year h 1 ' 
I T1 regard to the previous statements on moulting, see, on sa'P 1 , 
&c., Macgillivmy, ‘Hist. Brit. Birds,’ vol. iv. p. 371; on Glare 0 ’? 
curlews, and bustards, Jerdon, ‘ Birds of India,’ vol. iii. p. 615 , ’ 
683 ; on Totanus, ibid, p. 700 ; on the plumes of herons, ibhf 
73S, and Macgillivray, vol. lv. p. 435 and 444, and Mr. Stafford A llc ' 
in the ‘ Ibis,’ vol. v. 1863, p. 33. 
