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Show 42 SEXUAL SELECTION: BIRDS. PART II. 1 Macgillivmy, 'Hist. Brit. Birds,' vol. iv. 1852, p. 177-181. (;HAP. XI!l. LAW OF BATTLE. 43 "males of the wild musk-uuck (Oairina rnoschata); ''and where these fights have occurred the river " is covered for some distance with feathers." 8 Birds which seem ill-adapted for fighting engage in fierce ·conflicts ; thus with the pelican the stronger males ·drive away the weaker ones, snapping with their hnge beaks and giving heavy blows with their wings. Male snipes fight together, " tugging and pushing each "other with their bills in the most curious manner ·" imaginable." Some. few species are believed never to tight; 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." 9 The males of many birds are larger than the females, and this no doubt is an advantage to them in their battles with their rivals, and has been gained through sexual selection. The difference in size between the two sexes is carried to an extreme point in several Australian species; thns thfl male musk-duck (Biziura) and the male Oinclorarnphus cruralis (allied to our pipits) are by measurement actually twice as large as their respective females.10 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 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. 8 Sir R. Schomburgk, in 'Journal of R. Geograph. Soc.' vol. xiii. 1843, p. 31. 9 'Orl_l.i.thological Biography,' vol. i. p.l91. For pelicans and snipes, .sec vol. m. p. 381, 477. 10 Gould, 'Handbook of Birds of Australia,' vol. i. p. 395; vol. ii. p. 383. |