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How to Study Birds
THE NESTING SEASON
BY FRANK M. CHAPMAN
THIRD PAPER
The first evidence of the near approach of the nesting time among
hirds is furnished by the phenomena of the mating season.
filming Chief among these are song. and the sounds produced in
various ways which take the place of song. display of plu-
mage. fighting, dancing, and the numerous peculiar evolutions through
which birds give vent to their feelings at this period when their physical vigor is at its height.
As a rule, these exhibitions are given only by the male: and the question at issue is, are they simply expressions of the intense vitality of the season, or are they designed to attract the attention of the female, and thus aid the bird to win a mate? There is a wide field for study here; in fact, so few really sati. actory observations on the mating habits of wild birds exist that no conclusive explanations of the origin of their customs and costumes have been advanced.
Song is undoubtedly a means of announcing a bird‘s presence, and,I it is also a challenge, as well as a reply. to a rival. Nothing so stimulates song as song The crowing of cocks admirably illustrates this. While singing continues after a tnate has been secured. is not song ever addressed directly to the female? Are there never song contests among males. With a near-by. attentive female for the prize?
In fighting for a mate, action and cause are so closely related that the development of spurs, for instance, is generally attributed to that form of natural selection which brings success to the strongest, best-equipped fighter and enables it to transmit its own desirable characters to its off-
spring. This, however, is a matter primatin to be settled by the tnales. Two or more males meet, battle, and the victor gets the prize of a mate; but whether the mate has any voice in the matteri unknown. Conse— quently, in those more peaceful forms of sexual activity when rival males attempt to outdo each other through display of plumage. naturalists are not agreed whether these exhibitions are designed to please the female,—who presumably would then select the most attractive performer.—or whether
they are only a relief or outward expressicn to the emotions of the mating
season. Opportunities to make observations bearing on these questions are not
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