"The Arctic Terns illustrates one of the most fascinating of mysteries associated with birds. As in the case of many other species on land and sea, the young of the year undertake the southward migration weels ahead of the adults. How do they know the traditionnal migration routes unless they inherit their ancestors' memory of the geography involved ? The notion, however, that they do inherit knowledge that their ancestors have learned surpasses the bounds of genetic orthodoxy.
Most species of tern, including the Arctic, are airy-fairy creatures. Their tapering and pointed wings, reaching forward to the joint and then raked back, each V-shaped in silhouette, are too sharply angled for sailing flight. Neverthless, they provide an even greater excess of surface than those of gulls, just as those of gulls are proportionately more surgace than those of the Fulmar. One could say that, in normal flight, these bent wings flick with the regularity of a pulse, except that the word "flick" does not suggest the depht of each stroke. The wings snap down in successives strokes that rock the relatively small body between them. The bird may remain hanging in the wind, whipping it with the regular downbeats of its wings, forked tail spread and outer tail-feathers streaming wide - until, seeing a fish below, it suddenly dives vertically to pierce the water, from which it emerges a flight a moment later, its bill holding crosswise a shaving of silver that shimmers in its final efforts to swim."
The Storm Petrel and the owl of Athena, III, Louis J. Halle