100 SEXUAL selection: BIEDS. PartIL 



direct and indirect evidence. It is miicli more difficult 

 to decide what qualities determine the choice of the 

 females ; but here afrain we have some direct and in- 

 direct evidence that it is to a large extent the external 

 attractions of the male, though no doubt his vigour, 

 courage, and other mental qualities come into play. 

 We will begin with the indirect evidence. 



Length of Courtshi]p. — The lengthened period during 

 which both sexes of certain birds meet day after day 

 at an appointed place, probably depends partly on the 

 courtship being a prolonged affair, and partly on the re- 

 iteration of the act of pairing. Thus in Germany and 

 Scandinavia the balzens or leks of the Black-cocks, 

 last from the middle of March, all through April into 

 May. As many as forty or fifty, or even more birds 

 congregate at the leks ; and the same place is often fre- 

 quented during successive years. The lek of the Caper- 

 cailzie lasts from the end of March to the middle or 

 even end of May. In North America " the partridge 

 dances " of the Tetrao jyhasianelhis " last for a month 

 or more." Other kinds of grouse both in North Ame- 

 rica and Eastern Siberia^ follow nearly the same habits. 

 The fowlers discover the hillocks where the Euffs con- 

 gregate by the grass being trampled bare, and this shews 

 that the same spot is long frequented. The Indians of 

 Guiana are well acquainted with the cleared arenas, 

 where they expect to find the beautiful Cocks of the 

 Eock ; and the natives of New Guinea know the trees 

 where from ten to twenty full-plumaged male Birds of 



^ Nordmaun describes (' Bull Soc, Imp, des Nat. Moscow,' 1861, torn. 

 xxxiv. p. 264) the balzen of Tetrao urogalloides in Amur Land. He 

 estimated the number of assembled males at above a hundred, the 

 females, which lie hid in the surrounding bushes, not being counted. 

 The nois> s uttered dilfer from those of the T. urogallus or the caper- 

 cailzie. 



