seabirds such as Laysan albatrosses, Manx shearwaters, and several 

 tropical species of terns. Sooty and noddy terns reach their most 

 northern breeding point on the Dry Tortugas, off the southwest coast 

 of Florida. They are not known to wander any appreciable distance 

 farther north. Displaced breeding birds returned to their nests on the 

 Dry Tortugas after they had been taken on board ship, confined in 

 cages below decks, and carried northward 400 to 800 miles before 

 being released in a region where they had had no previous 

 experience. Likewise, Laysan albatrosses and Manx shearwaters 

 have returned over 3,000 miles in similar homing experiments. 



Possibly the "homing instinct," as shown by pigeons, terns, 

 shearwaters, albatrosses, and by the frigatebirds trained as message 

 carriers in the South Pacific, may not be identical with the sense of 

 perceptive orientation that figures in the flights of migratory birds. 

 Nevertheless, it seems closely akin and is probably governed by the 

 same mechanisms. There are good reasons to assume that once we 

 know the processes governing displaced homing we will know, in 

 general, how birds navigate; this question is still far from being 

 answered (Wallraff 1967). 



Some students have leaned toward the possible existence of a 

 "magnetic sense" as being the important factor in the power of 

 geographical orientation. The theory was conceived as early as 1855 

 and reported in 1882 by Viguier. Investigations of this have been 

 conducted by Yeagley (1947) and Gordon (1948) with contradictory 

 results. In 1951, Yeagley incorporated the idea that sensitivity to the 

 effect of the earth's rotary motion through the vertical component of 

 the magnetic field is the means of orientation. The basic question 

 asked of the theory is: "Can birds detect such minute differences in 

 the earth's magnetic field and can these forces affect bird behavior?" 



Attempts to demonstrate the effect of radio waves on the 

 navigational ability of birds have produced contradictory results. In 

 some of these tests, homing pigeons released near broadcasting 

 stations have appeared to be hopelessly confused, whereas in others, 

 apparently conducted in the same manner, no effects could be 

 discerned. Before sensitivity of birds to electromagnetic stimuli of 

 any kind can be accepted or rejected, much additional experimental 

 work is necessary. 



Human navigators have used the heavenly bodies in determining 

 their course and position for centuries. It would not be surprising 

 then to find other long-distance travelers using the same method. One 

 of the most constant visual cues a migrating bird could use would be 

 the sun's or moon's path and the location of the stars. 



Some of the more recent experimental work on bird navigation has 

 been with astronomical (sun) and celestial (star) directional clues. 

 Studies by Kramer, Sauer, and others have indicated a phenomenal 

 inherited ability in birds to use the position of the sun by day and the 

 stars by night to chart their courses. This involves an intricate 

 compensation for daily, seasonal, and geographical changes in the 

 positions of these heavenly bodies. Kramer (1957, 1961) placed 



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