3^2 The Descent of Man. Part IT. 



instance known to me in the case of birds, of any structure 

 serving as a shield. The ruff of feathers, however, from its 

 varied and rich colours probably serves in chief part as an orna- 

 ment. Like most pugnacious birds, they seem always ready to 

 fight, and when closely confined often kill each other; but 

 Montagu observed that their pugnacity becomes greater d-iring 

 the spring, when the long feathers on their necks are fully 

 developed ; and at this period the least movement by any one 

 bird provokes a general battle.' Of the pugnacity of web-footed 

 birds, two instances will suf&ce : in Guiana " bloody fights occur 

 " during the breeding-season between the males of the wild 

 " musk-duck (CaiViVia miischatu) ; and where these fights have 

 " occurred the river is covered for some distance with feathers." * 

 Birds which seem ill-adap'ed for fighting engage in fierce con- 

 flicts ; thus the stronger males of the pelican drive away the 

 weaker ones, snapping with their huge beaks and giving heavy 

 blows with their wings. Male snipe fight together, " tugging 

 " and pushing each other with their bills in the most curious 

 " manner imaginable." Some few birds are believec' never lo 

 fight ; this is the case, according to Audubon, with one ot ilie 

 woodpeckers of the United States (^ficus auratus), although " the 

 " hens are followed by even half a dozen of their gay suitors."' 



The males of many birds are larger than the females, and this 

 no doubt is the result of the advantage gained by the larger and 

 stronger males over their rivals during many generations. The 

 difference in size between the two sexes is carried to an extreme 

 point in several Australian species ; thus the male musk-duck 

 (Biziura) and the male Cincluraniphns cmralis (, allied to our 

 pipits) are by measurement actually twice as large as their 

 respective females.'" With many other birds the females are 

 larger than the males ; and as formerly remarked, the explana- 

 tion often given, namely, that the females have most of the work 

 in feeding their young, will not suffice. In some few cases, as 

 we shall hereafter see, the females apparently have acquired 

 their greater size and strength for the sake of conquering other 

 females and obtaining possession of the males. 



The males of many gallinaceous birds, especially of the poly- 

 gamous kinds, are furnished with special weapons for fighting 

 with their rivals, namely spui's, which can be used with fearful 



' MacgilliTi-av, ' Hist. Brit. i. p. 191. For pelicans and snipes, 



Birds,' vol. ir. 1852, pp. 177-181. fee vol. iii. pp. 138, 477. 



' Sir R. S.;lioinburgk, in '.lournal '" Gould, ' Handbook of Birds of 



jf R. Gcograph. Soc' vol. xiii, 1843, Australia,' vol. i. p. 395 ; vol. li. j) 



0. 31. 383 



' ' Ornitliolngical Cirgraphy,' vol. 



