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 apparently never pairs, its sexual relations 
may be described as representing a kind of promiscuous polygamy. 
