. [Articles about birds from National geographic magazine]. Birds. 92 THE NATIONAL GEOGRAPHIC MAGAZINE. Phutograph t^y Thomas Lileyler SOME OF man's most USIU'*UI< FEATriKRED FRIICNDS Gulls perform very real services as scavengers, keeping many a beach clear of dead fish and other refuse. They wander far up our rivers and even breed in large numbers on the lakes of the interior. his kind appeared no more until spots of bare ground became visible. MILLIONS MIGRATL AS SEASONS CHANGE The bird life of the United States is believed to total more than four billion in- dividuals. This means that m
. [Articles about birds from National geographic magazine]. Birds. 92 THE NATIONAL GEOGRAPHIC MAGAZINE. Phutograph t^y Thomas Lileyler SOME OF man's most USIU'*UI< FEATriKRED FRIICNDS Gulls perform very real services as scavengers, keeping many a beach clear of dead fish and other refuse. They wander far up our rivers and even breed in large numbers on the lakes of the interior. his kind appeared no more until spots of bare ground became visible. MILLIONS MIGRATL AS SEASONS CHANGE The bird life of the United States is believed to total more than four billion in- dividuals. This means that many hundred millions of migrants move north and south with the changing seasons. Though many go by day and may be seen by all who take the trouble to observe, vast numbers also pass by night. During the height of the spring migra- tion, those whose ears are attuned to Nature's voices may hear mysterious notes overhead, many of which may be recognized. They mark the course of winged travelers exidting in springtime vigor and approaching nuptials in the haunts which they seek toward the top of the world. Telescopes held on the moon at that time often reveal their silhouettes as they cross its face. In autumn the throng moves southward over a longer period, and the travelers wear the soberer garb of everyday life. Though it has been plain that migrat- ing species, in general, move north and south—the movements of some covering nearly or quite the entire length of the continent—yet only vague information on the subject has been available, since it was impossible to determine the movements of individuals. Through bird banding a method is now developed that will not only tell us where individual birds wan- der, but will enable us to trace their routes and determine the exact areas where they go in the north to rear their young or in the south to winter. We may also learn something concern- ing the strange, sporadic occurrence of l)irds in ]iarts of the world far distant from thei
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