that it is an old bird that leads the group. Where there is segregation 

 of the sexes, the young birds usually accompany their mothers, as is 

 the case with some of the ducks. After the females start to incubate 

 their eggs, the males of most species of ducks flock by themselves and 

 remain together until fall. 



The males and females of some species may migrate either simul- 

 taneously or separately. In the latter case it is usually the males that 

 arrive first, sometimes great flocks of male birds, as in the red-winged 

 blackbird, reaching a locality several days before any of the females. 

 This is particularly the rule in spring: The first robins are usually found 

 to be males, as are also the first song sparrows, rose-breasted grosbeaks, 

 and scarlet tanagers. This early arrival of the males has been ex- 

 plained on the theory of territorial possession, under which the male 

 selects the area where it elects to breed, each individual attempting to 

 protect a definite territory from trespass by other males of his own kind, 

 at the same time singing or otherwise announcing his presence and 

 inviting the later arriving female to examine the territory that he has 

 selected for nesting. The long-billed marsh wren is a noteworthy 

 example, and the males of this species may enthusiastically build sev- 

 eral dummy nests before the females arrive. 



In a few species the males and females apparently arrive at the breed- 

 ing grounds together and proceed at once to nest building. In fact 

 among the shore birds, ducks, and geese, courtship and mating may 

 take place in whole or in part while the birds are in the South or on 

 their way north, so that when they arrive at the northern nesting 

 grounds they are paired and ready to proceed at once with the raising 

 of their families. Mallards and black ducks may be observed in pairs 

 as early as January, the female leading and the male following when 

 they take flight. Naturally these mated pairs migrate north in com- 

 pany, and it was largely to protect such species that duck shooting in 

 spring was abolished by Federal law a number of years ago. 



Many shore birds nest well within the Arctic Circle, and it is the opin- 

 ion of ornithologists that most of these birds share, at least in part, the 

 habits of the phalaropes, a family in which the male assumes the entire 

 care of the eggs and young. If this be true, it explains why in southern 

 latitudes so many of the earliest fall arrivals are females that may have 

 deserted the breeding grounds after the eggs were laid. 



Migratory flights are frequently accomplished in close flock forma- 

 tion, as with the shore birds, blackbirds, and waxwings, and especially 



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