Mar., 1919 THE MARITAL TIE IN BIRDS 79 is an impartial mixture of sexes and of generations, in which the sociM tie dom- inates the other two, if these other two exist at all at the time. Are they really present? Will the flock coagulate in the spring and give out the same marital combinations that existed during the previous breeding season ? Is not parent just as liable to mate with its own offspring as with a member of its own gen- eration ? Consider the case of our non-social birds, such as the Shrikes and the Mockingbird. The asexual winter bird sees only a competitor in every other one bf his own species who invades the particular territory which he has pre- empted as his own. These birds are, with us here in the ?outh, more or less localized as to individuals; hence it doubtless often happens that, through pro- pinquity, the same combination of individuals may recur in successive years. But does this involve a marital constance ? I doubt it. Take again in the case of the migratory species. There is a separate mi- gration of the sexes in many of them. By the end of August most of the male Hooded Orioles have gone from the neighborhood of Los Angeles. There are still plenty of females and young of the year. The same might be said of the Black-headed Grosbeak and of a number of other species. The "men folk" have gone off on a regular stag party (or Elk's excursion) to the tropics. Will their "women folk" follow after with the children and hunt up their neglect- ful lords ? IVIay they not even winter in separate intra-tropical states, spend. ing the asexual part of their yearly cycle wholly unconscious of each other's being? On the return migration, the same separate .movement may be ob- served. The vagrancy impulse seems to attack the males first and they push northward in great pioneer armies of males. I have seen a flock of male gros- beaks flying like a flock of blackbirds and entirely unleavened by feminine presence. They were just arriving from the south. Did their last season's wives follow later and claim, each, her recalcitrant spouse ? Then there are cases of abject desertion on the part of the male. Such is true of the Anna Hummingbird. I have found many nests of this species, in various stages of progress of the nest or of its content, but never yet have I seen the marital tie survive the early stages of nest building. The female com- pletes the nest, incubates the eggs, and rears the young without assistance from the male. Mrs. Hummingbird is the original golf widow, with a husband some- where at the club, but she is not sure where (nor probably does she care). Perhaps we should not offer here as evidence the great variety of courting antics in which birds indulge, from the classic flight of the retiring woodcock to the dancing tournaments of the grouse. Are they merely for stimulus and not for selection of the mate ? If birds mated for life would we see these court- ing activities so commonly .? They would be needed only by the young and by the bereaved. The theorist, however, feels it proper to ask the question: Are there not biologic reasons why a seasonal readjustment of the marital relation would prove advantageous to the race ? If a protracted effort is required each season before a mate is obtained, the less virile bird will go unmated. Would not the result average better for the maintainante of tone in the race ? Whatever else may be claimed for the principle of sexual selection, it seems to be more or less vital to racial vigor. Seasonal recurrence of the selective process would then be classed as a sort of protective adaptation in a class of animals showing abundant specialization in other respects.
