I will end this chapter by relating, with as much detail as is possible, the curious family history of the Adélie penguins;[46] as these birds have developed some interesting and startling experiments in nursery care and parenthood. The penguins live in large social colonies. It should be noted first that the death rate among the young birds is enormously high, as happens invariably where the single family is replaced by great breeding colonies. Yet the penguins are self-sacrificing parents. Year by year in the month of October they return to the same breeding-ground, having travelled many hundreds of difficult miles, and urged by a mysterious nostalgia that their children may be born in the same home. The first duty is to take possession of one of the old stone nests, or to scoop out a new hollow in the ground. Here the hens sit by the future home, and wait for proposals from the cocks. The advance is made by what appears to be a symbolic action and the cock places a stone at the hen’s feet. But often the hen answers never a word. Bloody duels are fought between rival suitors to arouse her passion and prove the vigour of her mate. Both birds work at the home-making, repairing an old nest or forming a new one, which is made of rounded stones. The cock collects these, and it is interesting to note what would seem to be an æsthetic taste in these bird-builders; certain painted pebbles, provided by the explorers for the use of the birds, were in great demand, the colour red being preferred to green. During the first days of wedded life the conflicts between the cocks continue, and the chosen cock maintains his rights by driving off all interlopers; but later, when the pair settle down to the serious duties of the family, they live in peace and are perfectly faithful to each other. Not until the eggs have been laid does either parent go to feed; the shortest period of total abstinence from food being about eighteen days and the longest about twenty-eight days—a fine example of parental sacrifice. Then one of the birds marches off to the water for a holiday, which may last from seven to ten days, after which it comes back to give the other bird its turn. When the young penguins are hatched the parents share in the work of feeding and guarding them, and relieve each other at frequent intervals. The bird who goes to feed always returns heavily burdened with provisions, and its always quaint shape becomes grotesque, when so laden with crustaceans that it has to lean backwards to keep its balance. Sometimes a bird will try to carry too much, with the result that it tumbles over and loses the entire load. The young chicks feed in the same way as the young cormorants, by thrusting their heads into the parent’s gullet.