New Britain herald., 1927-01-11
NO ONE CAN EXPLAIN WHY BIRDS MIGRATE
Expert Baked by Habits Of Lifelong Feathered Friends

Washington, D. C., Jan. H.
 Scientists can only guess at the
 meaning of the arrival of the first robin in the spring or the south- ward flight of geese across the late autumn sky. in the opinion of Dr. Alexander Wetmore, assistant secre- tary of the Smithsonian institution, and president of the American Ornithologists Union. Behind migra- ton lie such a multitude of causes, men have been unable to ascertain the truth.
 Studied Birds For Years
 Constantly student of bird life, Dr. Wetmore has made special studies in the Salt Lake Valley, the Bighorn Basin in Wyoming, the pampas of Argentina, the coasts of Uruguay, the sand dunes of Buenos Aires, any many other vantage points throughout the western hemisphere. Dr. Wetmore has written book on the migrations of birds, just pub | ilSHtu, III NlllCli IS SulliS uP jllS ptl sonal observations and correlates them with the findings of ornitholo- cists for the past 200 years, with the result that a number of misunaer- standings concerning bird life are cleared up.
 "The entire act of migration is so utterly complex that no single factor may be ascribed as the absolute cause" Dr. Wetmore states, but he takes as his hypothesis that migra- ton has arisen from movements in duced by seasonal and climatic changes in certain species until it has become hereditary instinct, "a part of the life-cycle of the individ- ual," and now actuated by physiologi- cal conditions. The habits of ages have become so well fixed that weather conditions now have little to do with the migrations of birds, eX- cept to permit them to travel or hold them back, as the cast may be. Redstarts wintcring in the West Indies, or wagtails spending the cold season in central Africa, notice no difference in temperature or climate conditions between November and April, yet in the latter month they regularly move north toward the summer home.
 Some Night Pliers, Some Day
 In such matters as the speed of | flight of birds, the time of migration, lines of migration, sense of direction, . and mortality among migrant birds, | Dr. Wetmore sets down many inter- sting facts. Large birds, such as | looms, cranes, ducks and hawks regu- larly fly by day, while the majority of small birds, such as warblers, fly ] catchers and sparrows fly by night. The chief factor here is the necessity on the part of the smaller birds to seek they food by day, and not fear of attack in day flight. Fasting for q day is no hardship for many of the larger birds.
 Migrating birds commonly fly at an altitude no higher than 5000 feet. slthough birds of strong flight have been known to reach an altitude Of 1000 feet. Contrary to common belief, flight becomes increasingly difficult as the bird rises above 5000 feet Birds commonly fly against or across a wind current, and are up- set if they fly with q strong wind. As to the speed of birds, Dr. Wetmore destroys a number of illusions. The smaller perching birds fly at 20 to 37 miles per hour, while ducks and geese range from 42 to 59 miles. Most birds are probably capable of Doubling their normal speed for Bhort distances. but the greatest speed recorded was that of the com mon swift Of Eurasia, observed from m airplanes to be maleing 70 mSles in hour In normal fligtt.
 Unfailing Sense of Direction
 The ability of birds to maintain directions unfailingly and to return .ear after year to the same spot
 rom great distances, as many do, is tscribed by pr. Wetmore to sense Df direction which is no more eX-