This last case affords a striking illustration of the real object of all these elaborate movements. The male albatross, an ugly and dull-coloured bird,[66] during courtship stands by the female on the nest, raises his wings, spreads his tail, throws up his head with the bill in the air, or stretches it straight out or forwards as far as he can, and then utters a curious cry.[67] But the most interesting example that I have been able to find recorded of dancing among birds is the habit of waltzing, common to the male, and in a lesser degree to the female ostrich. It is thus described by S. Cronwright Schreiner.[68] "After running a few yards they (the ostriches) will stop, and with raised wings spin round rapidly for some time until quite giddy, when a broken leg occasionally occurs.... Vigorous cocks 'roll' when challenging to fight or when wooing a hen. The cock will suddenly bump down on his knees (ankle joints), open his wings, and then swing them alternately backwards and forwards as if on a pivot. At such a time the bird sees very imperfectly, if at all, in fact he seems so preoccupied that if pursued one may often approach unnoticed. Just before 'rolling,' a cock, especially if courting a hen, will often run slowly and daintily on the points of his toes, with neck slightly inflated, upright and erect, the tail half dropped and all his body feathers fluffed up; the wings raised and expanded, the inside edges touching the sides of the neck for nearly the whole length, and the plumes showing separately like an open fan. In no other attitude is the splendid beauty of his plumage displayed to such advantage." In this case it is very suggestive to find that it is the male ostrich who takes upon himself the task of hatching and rearing the young. Perhaps this accounts for the female ostrich being able to dance as well as the male. There are very few examples of birds who are bad fathers. Often the male rivals the female in love for the young; he is in constant attendance in the vicinity of the nest; he guards, feeds and sings to the female, and sometimes shares with her the duty of incubation. This is done by the male wood-pigeon, missel-thrush, blue martin, the buzzard, stone-curlew, curlew, dottrel, the sandpiper, common gull, black-coated gull, kittiwake, razorbill, puffin, storm-petrel, the great blue heron and the black vulture. Among these birds it is usual for the family duties to be performed quite irrespective of sex, and the parent who is free takes the task of feeding the one who is occupied. As soon as one family is reared many birds at once burden themselves with another. Audubon records the case of the blue bird of America, who works so zealously that two or three broods are reared at the same time, the female sitting on one clutch, while the male feeds the young of the preceding brood.[69]