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 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 company, and it was largely to protect such species that duck shooting in spring was abolished by Federal law several, years ago. Many shore birds nest well within the Arctic Circle, and it is the opinion 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 formation, as with the shore birds, blackbirds, and waxwings, and especially some of the sparrows--the snow buntings (_Plectrophenax nivalis_), longspurs, juncos, and tree sparrows (_Spizella arborea_). Other species, however, though they travel in flocks, maintain a very loose formation; examples are the turkey vultures (_Cathartes aura_), the hawks, swifts, blue jays, swallows, warblers, and bluebirds. Still others, the grebes, great horned owls (_Bubo virginianus_), winter wrens (_Nannus hiemalis_), shrikes, and belted kingfishers (_Megaceryle alcyon_), for example, ordinarily travel alone, and when several are found in close proximity it is an indication that they have been drawn together by unusual conditions, such as abundant food. =WHERE BIRDS MIGRATE= DISTANCES OF MIGRATION VARY Definite evidence shows that both the length and the duration of the migratory journey vary greatly. The bobwhite and the western quails, the cardinal (_Richmondena cardinalis_), the Carolina wren (_Thryothorus ludovicianus_), and probably some of the titmice and woodpeckers, which are apparently nonmigratory, may round out their full period of existence without at any time going more than 10 miles from the nest where they were hatched. SHORT AND UNDETERMINED MIGRATIONS