red-backed shrikes are known to migrate ahead of their young. 



In contrast to this loss of parental concern, geese, swans, and cranes 

 remain in family groups throughout migration. The parent birds 

 undergo a wing molt that renders them flightless during the period 

 of growth of their young so that both the adults and immatures 

 acquire their flight capabilities at the same time and are able to start 

 south together. Large flocks of Canada geese, for example, are 

 composed of many families banded together. When these flocks 

 separate into small V-shaped units it is probably correct to assume an 

 old goose or gander is leading the family. After female ducks start to 

 incubate their eggs, the males of most species of ducks flock by 

 themselves and remain together until fall. When segregation of the 

 sexes such as this occurs the young birds often accompany their 

 mothers south. Murray and Jehl (1964) concluded from mist-netting 

 many thousands of migrant passerines at Island Beach, New Jersey, 

 that adults and juveniles travel at approximately the same time. 



By Sex 



Males and females of some species may migrate either 

 simultaneously or separately. In the latter case it is usually the males, 

 rarely the females, that arrive first. Sometimes great flocks of male 

 red-winged blackbirds reach a locality several days before any 

 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. In Europe, the three 

 buntings mentioned previously are also segregated as to sex during 

 migration. Figure 8 shows two prominant peaks for both the 

 Cretzschmar's and Ortolan buntings; during passage the first peak 

 was primarily males while the second peak consisted mostly of 

 females. This early arrival of males on the breeding grounds is 

 associated with territorial possession whereby the male selects the 

 area where it intends to breed and each individual attempts to 

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

 kind, while announcing his presence to rival males and later arriving 

 females by song or other display. The female then selects the site 

 where she wishes to nest. The long-billed marsh wren is a noteworthy 

 example; the males may enthusiastically build several nests before 

 the females arrive. In the fall, common and king eiders are sexually 

 segregated during migration. During July, flocks crossing Point 

 Barrow are composed almost entirely of males, while after the 

 middle of August the flocks are almost all females (Thompson and 

 Person 1963). In the Chicago area, Annan (1962) reported that some 

 males, such as the hermit thrush, Swainson's thrush, gray-cheeked 

 thrush, and veery, arrive before any females and predominate 

 during the first week of occurrence. 



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

 breeding grounds together and proceed at once to nest building. In 

 fact, among shorebirds, ducks, and geese, courtship and mating 

 often takes place in whole or in part while the birds are in the South or 



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