SEXUAL SELEOTIOy 606 



both tbeir summer and winter plamage; but the male 

 undergoes a greater amount of change at each recurrent 

 season than the female — of which the ruff {Machetes pug- 

 nax) offers a good instance. 



With respect to the cause or purpose of the differences 

 in color between the summer and winter plumage, this may 

 in some instances, as with the ptarmigan," serve during both 

 seasons as a protection. When the difference between the 

 two plumages is slight, it may perhaps be attributed, as 

 already remarked, to the direct action of the conditions of 

 life. But with many birds there can hardly be a doubt that 

 the summer plumage is ornamental, even when both sexes 

 are alike. We may conclude that this is the case with 

 many herons, egrets, etc., for they acquire their beautiful 

 plumes only during the breeding season. Moreover, such 

 plumes, topknots, etc., though possessed by both sexes, 

 are occasionally a little more developed in the male than 

 in the female; and they resemble the plumes and orna- 

 ments possessed by the males alone of other birds. It is 

 also known that confinement, by affecting the reproductive 

 system of male birds, frequently checks the development 

 of their secondary sexual characters, but has no immediate 

 influence on any other characters; and I am informed by 

 Mr. Bartlett that eight or nine specimens of the Knot 

 {Tringa canutus) retained their unadorned winter plumage 

 in the Zoological Gardens throughout the year, from which 

 fact we may infer that the summer plumage, though com- 

 mon to both sexes, partakes of the nature of the exclusively 

 masculine plumage of many other birds." 



" The brown mottled summer plumage of the ptarmigan is of aa mneh im- 

 portance to it, as a protection, as the white winter plumage ; for in Scandinavia, 

 during the spring, when the snow has disappeared, this bird is known to suffer 

 greatly from birds of prey, before it has acquired its summer dress : see Wil- 

 helm von Wright, in Lloyd, "Game Birds of Sweden," 1867, p. 125. 



*> In regard to the previous statements on moulting, see, on snipes, etc., 

 Macgillivray, "Hist. Brit. Birds," vol. iv. p. 371; on Glareolte, curlews, and 

 bustards, Jerdon, "Birds of India," vol. iii. pp. 616, 630, 683; on Totanua, 

 ibid p. 700; on the plumes of herons, ibid., p. 738, and Macgillivray, vol. iv. 

 pp 435 and 444, and Mr. Stafford Allen, in the "Ibis," vol. v., 1863, p. 33. 



