Much to Learn

◆ Scientific investigators world wide have long pondered the question of how birds are able to navigate over great distances. In some respects birds seem to follow certain features of the topography, such as a coastline or mountain chain. But obviously more than that is involved, for migratory birds sometimes cross huge bodies of water or continue their migration at night when prominent land features are indistinguishable. How do they do it?

In the 1950’s a German scientist showed by experiments that some birds use the sun’s position as a means of guidance. Experiments even demonstrated that birds seem to have an internal biological clock enabling them to compensate for the apparent movement of the sun across the sky.

As to migratory birds at night, it appears that the stars are used. Some birds locate one star or a group of stars and fly at a certain angle relative to it. As with the daytime traveler steering by the sun, these birds at night adjust the angle of flight with respect to the stars by an internal sense of timing. Other birds seem to use a constant pattern of stars, just as a human might sight along the Big Dipper in locating the North Star.

Regarding the marvelous ability of birds to navigate in such ways, Dr. Stephen Emlen, an associate professor of animal behavior, observed: “Many persons point to such studies and conclude that the mysteries of animal navigation have now been solved. This is not true. Current theories fail to tell us how or why an animal selects one direction over another. And recent evidence indicates that star and sun cues may not even be essential for some migrants.” Thus, some birds seem to be able to navigate at night under total overcast or even when flying between cloud layers. Dr. Emlen added: “This does not disprove that birds use celestial information, but it certainly implies that they may also use other cues for directional guidance. We do not know what these cues may be. Might a bird use the wind as a cue? Might some even orient by the earth’s magnetic field? Recent studies suggest both of these possibilities. Perhaps one day we shall know. . . . We still have much to learn.”