THE DIMENSIONS OF TRAVEL 



Matthews (1951a, b; 1952; 1953a, b; 1955a, b)* and Kramer (1952, 

 1953 ) have shown in pigeons and ( Matthews' studies ) in several species of 

 gull and shearwater that there is a pattern of orientation toward home when 

 birds are given freedom in unfamiliar terrain. This direct orientation, Mat- 

 thews demonstrated, functions only when the sun is in view, and Matthews 

 has erected a hypothesis of sun navigation that hinges on the traveling 

 bird's awareness of change in arc and schedule relative to arc and time at 

 home. Moreover, with pigeons, Matthews (1955b: 78) has shown how this 

 ability to orient homeward from unfamiliar country varies according to the 

 distance from home. At a distance of between 20 and 40 miles "there would 

 seem to be a ring of country," Matthews observes, "in which birds would 

 have no direct orientation and presumably have to fall back on random 

 search methods. . . . Beyond 50 miles there is suggestive evidence that the 

 accuracy of orientation increases with distance, though this is not so firmly 

 established." This same "distance effect," as Matthews calls it, has puzzled 

 other workers, like Wodzicki and Wojtusiak ( 1934 ) in a study of swallows, 

 and Griffin (1943) in a study of terns and gulls. They noticed that birds 

 released distantly tended to return home more rapidly than others set free 

 in strange country within a shorter radius of home. This "distance effect" 

 favors the idea of sun navigation. Although able to perceive direction from 

 the sun on local range (like Kramer's caged Starlings), birds, like men, 

 may have no awareness of the change of the sun arc relative to earth and 

 time when close to home, and they must search for familiar surroundings 

 if lost. But, so the evidence suggests, the farther birds travel from home, 

 the more keen their awareness of the ever-increasing change of the sun's 

 arc and schedule relative to home. Hence, we presume, the longer a bird's 

 journey, the keener its awareness of the direction homeward even when 

 displaced from familiar surroundings. 



If birds are, indeed, able to navigate by the sun, as the pioneering studies 

 of Matthews and Kramer suggest, and if awareness of the sun as a nagiva- 

 tional cue is directly proportionate to the distance and velocity of travel, 

 then the swiftly flying Canvasback (traveling the 300 miles from Delta to 

 Lake Christina in 5 hours) has in orienting itself a distinct advantage over 

 a man on foot (walking 20 miles in 5 hours). Though for the purpose of an 

 objective study of migration we may make comparisons based on the rela- 

 tive coordinates of travel, the additional element of sun-awareness, then, 



See Matthews ( 1955b ) for the complete bibliography of Matthews and Kramer and for a 

 discussion of sun navigation. 



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