358 THE DESCENT OP MAN. 



great ruff of feathers round the neck is then erected, and accord- 

 ing to Col. Montagu "sweeps the ground as a shield to defend the 

 "more tender parts;" and this is the only 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 colors probably 

 serves in chief part as an ornament. Like most pugnacious birds, 

 they seem always ready to fight, and when closely confined often 

 kill each other; but Montagu observed that their pugnacity be- 

 comes greater during 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 suIHce: in Guiana "bloody 

 "fights occur during the breeding-season between the males of the 

 "wild musk-duck (Cairina moschata) ; and where these fights have 

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

 Birds which seem ill-adapted for fighting engage in fierce conflicts; 

 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 push- 

 "ing each other with their bills in the most curious manner im- 

 "aglnable." Some few birds are believed never to flght; .this is the 

 case, according to Audubon, with one of the woodpeckers of the 

 United States (Picus 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 (Bi- 

 ziura) and the male Cincloramphus cruralis (allied to our pipits) 

 are by measurement actually twice as large as their respective fe- 

 males." With many other birds the females are larger than the 

 males; and as formerly remarked, the explanation often given, 

 namely, that the females have most of the work in feeding their 

 young, will not sulHce. 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 polyg- 

 amous kinds, are furnished with special weapons for fighting 



' Macgillivray, 'Hist. Brit. Birds,' vol. iv. 1852, pp. 177-181. 



8 Sir R. Schomburgli, in 'Journal of R. Geograph. Soc' vol. xiii. 1843, 

 p. 31. 



» 'Ornithological Biography,' vol. i. p. 191. For pelicans and snipes, 

 see vol. iii. pp. 138, 477. 



'o Gould, 'Handbook of Birds of Australia,' vol. i. p. 395; vol. ii. p. 383. 



