70 COURTSHIP 



Courtship. The first evidence of the near approach of the nesting- 

 season among birds is furnished by the phenomena of courtship. Chief 

 among these are song and the sounds produced in various ways which 

 take the place of song; display of plumage, fighting, dancing, and other 

 often remarkable activities through which birds give vent to their 

 emotions at this period of maximum vitality. As a rule, these vocal or 

 physical exhibitions are given by the male; and the question at issue is, 

 are they simply expressions of irrepressible vigor or are they designed 

 to attract the attention or stimulate the interest of the female and thus 

 aid the bird to win a mate. 



The function of song is discussed in another chapter, but in fighting 

 for a mate, action and cause are so closely connected that the develop- 

 ment of spurs, for instance, is generally considered a result of that 

 form of natural selection which awards success to the strongest, best- 

 armed fighter and enables it to transmit its own desirable characters to 

 its offspring. This matter is, however, primarily to be settled by the 

 males. Two or more males meet, battle, and the victor gets the prize 

 of a mate; but has this mate any voice in the matter? In those more 

 peaceful contests where rival males attempt to outdo one another 

 through display of plumage or violent actions, it is even more difficult 

 to decide to what extent the female is influenced, but it seems probable 

 that there is less actual selection than passive acceptance on her part 

 of the male which is most active in battle or display. 



It is much less difficult to make observations in this field than to 

 interpret them. What, for example, is the significance of the squabbles, 

 struttings and irrepressible vociferousness of the English Sparrow when 

 courting? 



Most of our birds are monogamous and doubtless take a new mate 

 for each nesting season; but some of the larger birds, notably among the 

 Hawks and Owls, are known to be more constant and are believed to be 

 mated for life. In either case, however, the mate, if lost, is usually 

 soon replaced, at least in the earlier stages of the nesting-season. 



Exceptions to the rule of monogamy are shown by the Anis (Croto- 

 phaga) which are communistic, and by certain species which are polyg- 

 amous. The Anis live in small flocks throughout the year. The 

 females lay in a common nest and all share the family duties. 



Among our North American birds the Wild Turkey is polygamous, 

 though all association with the female ceases after incubation begins, 

 while the male of the Prairie Hen and of some other members of the 

 Grouse family are said to have more than one mate. The Great-tailed 

 Grackle in Mexico has, at least, as many as five or six wives, and our , 

 Red-winged Blackbird has been suspected of Mormonism. 



The males of our Cowbirds are believed to outnumber the females, 

 and as this parasitic species apparent^ never pairs, its sexual relations 

 may be described as representing a kind of promiscuous polygamy. 



