BIRD MIGRATION

Press, Volume LXXIV, Issue 22492, 29 August 1938, Page 4

BIRD MIGRATION

EFFORT TO ESTABLISH

CAUSE

RESULTS OF EXPERIMENTS

IN ALBERTA

“Neither speculation nor simple observation can elucidate the immediate causes of bird migration,” said Mr R. A. Falla, curator of the CanterburyMuseum, in an address to the Society for Imperial Culture on Saturday evening. The modern study of bird migration, he said, included careful scientific experiment. Gilbert White, the early English naturalist, believed that when swallows disappeared from England in the wintey they did not leave the country, but hibernated there, hiding themselves in the mud. This represented the speculative stage of the study. Later, careful observation established the facts of bird migration—the distances, directions, and seasons. As an example of the modem experimental method, Mr Falla cited the work of Professor Rowan, in Alberta. This scientist observed that birds of a certain species, the junco, migrating north in spring, had an excessive development of certain glands (gonads, or sex glands), and of internal secretion. The birds moved south in autumn with both these developments much reduced. Beginning with the hypothesis that increasing or decreasing daylight might be the cause of migration, _ Professor Rowan subjected captive birds to an artificial decrease of daylight in a spring season. When released, these birds flew south, instead of north. To test whether the light itself was the direct cause of the glandular development, the scientist experimented further by decreasing the light daily, and at the same time keeping the birds exercised on moving perches. These birds, in spite of the decreasing light, flew north when they were released, showing that it was increased activity, and not light, which directly brought on the characteristic spring condition of the birds.