The Birmingham age-herald., 1915-08-21
Garrett P. serviss in the Spokane

Garrett F. Serviss in the Spokane
 Spokesman Review.
 nHE bird is an older inhabitant
 than man on earth and could
 . tell us many things about the history of our globe of which we have only an inferential Knowledge. Bird migration-one of the most impenetra- ble mysteries of terrestrial 1ife-may be a direct result of the invasion of ice ,n the glacial ages.
 When the bobolink, for instance, quits the New England fields with the oncoming of autumn and goes to South America to pass the winter, or rather not lose the summer, he is obeying an impulse come down to him through generations of his ancestors from the tune when their original northern home began to lose its permanently genial climate. Such, at least, is one of the most suggestive theories invented to explain bird migration.
 As the ice gradually pushed farther and farther southward it's advance edge swung back and forth with the seasons. and the birds acquired a habit of re- tiring and returning in a similar swing. Finally they were driven entirely from their old northern haunts. But with the end of the last glacial period the favorable conditions returned in tLe lands from which they had been ex- Lelled and they resumed possession But then the habit of seasonal migration had become so fixed that it was per ulanently retained, even in cases where it might have been abandoned, and the discovery having been made, under com- pulsion as it were, that summer con- ditions can always be obtained by pass l ing to and fro across the equator, this ! became the settled custom of many species of birds, whose sole home had
 once been in the north.
 diametrically opposite theory as. sumes that the original home was in
 the south, but in either case the gla- cial periods are regarded as having l furnished the motive for migration. l The results of the most extensive study of bird migration that has vel been made are embodied in a recent bulletin of the biological survey of the
 department of agriculture. The phe- nomena of migration would be more
 spectacular, and better known, if mosl of the birds did not confine their figh' Ito the night hours When nearly all tic tworld around them is asleep they ns silently for hours through the dark ness. One of the most remarkable cor. lclusions of the biological bureau Is that migrating birds pay no attention to the weather in choosing the time of theii 1 departure. The impulse seems to come
 from within and to be due to physio-
 logical causes related to the period Of l breeding.
 l Few birds put themselves to higi I speed during the migration flight. The, go such moderate distances as 20. 30
 40 miles a day, making many side ex- cursions for food which increases the
 actual space traversed. But some species
 make long continued and rapid flights
 Some make the trip across the Gulf oi
 Mexico. varying in distance. according ltc the route. from 500 to 700 miles. in {
 single trip. The purple martin is sais to average 120 miles every night in iti spring trip from Texas to Winnipeg.
 But whether they travel fast or slow many birds cover thousands of mile in each migration. north or south. Tn, I brilliant scarlet tanager spends hal the year in the United States and Can
 ada, and the other half In Peru. Nor