MIGRATORY BIRDS

Poverty Bay Herald, Volume LX, Issue 18036, 13 March 1933, Page 10

MIGRATORY BIRDS

UNSOLVED MYSTERIES THE LINE OF FLIGHTS The ends served, the cause or origin of the custom, the immediate stimuli on the individual in migration of New Zealand birds, were dealt with in up interesting manner by Mr. E. F. Stead, in ail address to the first meeting of the 1933 session of the Philosophical Institute of Canterbury. The lecturer quoted from many authorities. and stated that there were liiany mysteries connected with migration that had not been definitely explained. So far they were merely subjects ot theory. Birds migrated principally in the Northern Hemisphere for the reason that large areas of land were open for Hie greater part of the year, lie said. Indeed. migrating birds enjoyed a perpetual summer. Certain weather conditions caused the birds to move according to researches, but they had to ho in a proper physical condition to start Uf before the ur"P was effective. The birds rarely followed a straight course, and thov flew at heights of from a few yards to 8500 ft. Birds met with above 5000 ft. were the exception, and not the Mile. They did not hesitate to cross mountain ranges; for instance, thousands crossed the Himalayas. In speed they ranged from 25 to 50 miles an hour, hut there were known cases of much higher speeds. j PART PLAYED BY VISION Many theories had been pat forward as to now the birds kept to the right path. Vision played a part, for birds sometimes became lost in foggy weather ; on the other hand, vast numbers were able to proceed safely and surely when it was impossible to see what was below. It was quite possible that the birds possessed some special faculty of vision denied to the human. The homing of pigeons seemed to demonstrate that sight played an important part in direction finding, at least in that species. However, the homing of pigeons could not he regarded as a parallel to the action of migrating birds generally. Some migrations might well be of sudden growth, said Mr. Stead. The blight birds of Southland were the only migratory birds 6f New Zealand in the true sense of the word. Considerable numbers of the New Zealand dotterel migrated to Australia, taking a route via Auckland, Norfolk Island, Lord Howe Island, South Queensland, New South Wales, and along the south coast. This seemed to indicate that their early ancestors found that route easiest in the days when New Zealand was a part of Australia. ACTIVITIES OF THE YOUNG Godjwits arrived on their breeding grounds at the end of May, and left in August. 'Some of their young were only 17 days old when they began their migration. It was not unusual for birds to be blown off their course. The shining cuckoo wintered in the Solomon Islands, according to one authority. It was certain that few remained in New Zealand for the winter. Penguins, Mr. Stead said, spent many months in the sea. They were peculiarly adapted to an aquatic life, and they were able to regain their breeding grounds after having been hundreds- of miles away. Young birds definitely possessed an inherited memory of sonic sort. It might bo an instinct, but it accounted for the fact that birds were able to fly over a course that had been covered by their parents. Even this, however, could not account for the exact minuteness of the penguin’s sense of direction. As to the petrel family,' mutton birds had been “ringed” by the light-keener at Puysegur Point,, and subsequently they were found in northern California. They wintered in the far north of tho Pacific, and returned south in the spring. Moreover, they found their way across wide stretches of ocean far better than well trained navigators.

Mr. Stead concluded his address by stating that the general lack of data was so great that it was impossible even to theorise on the migration of the birds of New Zealand.