100 
SEXUAL SELECTION : BIEDS. 
PABI ^ 
direct and indirect evidence. It is much more difib’ 1 * * * * * ^ 
to decide what qualities determine the choice oi \ 
females ; but here again we have some direct and 1 
direct evidence tliat it is to a large extent the extern * 1 
attractions of the male, though no doubt his vig° n * 
courage, and other mental qualities come into pi 9 ?* 
We will begin with the indirect evidence. 
Length of Courtship . — The lengthened period dun"' 
which both sexes of certain birds meet day after dW 
at an appointed place, probably depends partly on 
courtship being a prolonged affair, and partly on the f® 
iteration of the act of pairing. Thus in Germany al1 
Scandinavia the balzens or leks of the Black-cock* 1 " 
last from the middle of March, all through April 
May. As many as forty or fifty, or even more bn ' 1 
congregate at the leks; and the same place is often b L 
quented during successive years. The lek of the Cap e '’ 
cailzie lasts from the end of March to the middle 
even end of May. In North America “the partri'-sj 
dances” of the Tetrao phasianellus “last for a mo® 
or more.” Other kinds of grouse both in North A 11 .' 1 ” 
rica and Eastern Siberia 1 follow nearly the same hab* 
The fowlers discover the hillocks where the Buffs c °^ 
gregate by the grass being trampled bare, and this sb e "j 
that the same spot is long frequented. The Indian® 
Guiana are well acquainted with the cleared are*"^, 
where they expect to find the beautiful Cocks of 1 1 . 
Bock; and the natives of New Guinea know the B'b 
where from ten to twenty full-plumaged male Bh' ( b 
1 Nordnmnn describes Bull. Soc. Imp. des Nat. Moscow,’ 186b ^ 
xxxiv. p. 2(14) the balzen of Tetrao urogalloides in Amur Laud- ^ 
estimated the number of assembled males at above a hundred) i 
females, which lie hid in the surrounding bushes, not being cou® - 
The noises uttered differ from those of the T. urogutlm or the 
cailzie. 
