THE NATURALIST.

Otago Witness, Issue 2371, 10 August 1899, Page 54

THE NATURALIST.

Ages of Birds-. The Ibis lias an interesting and useful article by Mr J. H. Gurney on the ages to which birds live. It is only possible at present to collect data from the duration of lives of birds in captivity ; evidence otherwise must be very unreliable, and it is purely a matter of theory as to whether the natural possible life is greater than under Jie unnatural conditions of captivity. There are records of a nightingale having lived 15 years, a thrush 17, a blackbird that was still alive at 20£, a goldfinch 23, and skylarks of 24- and 20. Ravens, owls, and cockatoos are popularly supposed to live to a very great age, and the following records appear to be authentic: — Raven 50, grey parrots 50 and 40, blue macaw 6*, eagle owl 53, and one still alive at 68. Some aquatic birds appear to live to a ripe old age, for we hear of a heron of 60, goose 80, mute swan 70. It is doubtful whether any of the fore-

going ages arc- any true guide as to the longevity of the actual families the birds represent, or, indeed, whether the possible age of one family exceeds that of another; but the records are interesting, and form a step in the ladder of investigation of this most difficult question. Mr Gurney makes the statement that the colouring of a bird in perfect health and the texture of its feathers are exactly the same at 50 as at five, and that those signs that are popularly put down to age, such as bleached and faded plumage and misshapen claws or beak, are attributable to unnatural conditions of some kind. The great tenacity of life some birds possess when deprived of food is marvellous, and the following instances are given: — Golden eagle, 21 days ; an eider duck, 28 ; an albatross, 35 ; and a penguin (Aptenodytes), it is stated, can live two months. Animals That Keep Guard. — It is well known that many animals appoint one or more of their lvumbei to act as sentinels to guard against surprise while the rest are asleep, or feeding, or at play. Among the animals — using the word in its wide3t sense — that are thus prudent may be named the following: — "Wasps, ants, chamois and other aixtelopes, prairie dogs, wild horses, rooks, swans, Australian cockatoos, zebras, quails, certain monkeys, flamingoes, New Zealand silver-eyes, shags, and other birds, marmots, mouflon and other sheep, seals, African wild cattle, huancoes, elephants, etc. Moles v. Men.— Mr Richard Lyddeker, the naturalist, states that he has traced a tunnel made by a mole in a single night for a distance of 100 yds. He calculates that in order to perform equivalent work a man would have to excavate in a single night a tunnel 37 miles long, and of sufficient size to permit him to walk through it. It may be recalled that William of Orange lost his life through the stumbling of his horse over a mole hill. • After that the English and Irish "Jacobites used to drink "to the little gentleman in the brown velvet coat." To Fight the Eagles.— ln Foula, one of the Shetland Islands, the natives make a business of rearing skau gulls in ordei to rid the' island of the eagles that congregate there and commit many depredations. The magnificent red sandstone cliffs that skirt the north-western coast became a favourite haunt of the eagles, and in this inaccessible spot they increased so rapidly that they became a terror to the farmers and fishermen who dwell on this isolated spot. The skau gulls are also strong and fierce, and the inveterate foe of the eagle. In battle the, gulls are nearly always victorioxis, and so the inhabitants of Foula hit upon the novel plan of feeding and caring for the skau gulls, which, though formidable to their feathered enemies, are very peaceful and docile when brought in contact with man.