MIGRATIONS OF WATERFOWL 



edge by an obliging little wonder, then all scientific research becomes a pure 

 farce." 



All through the ages of wondering, man has conceived the idea that the 

 answer to this mystery of avian orientation might be found in a single ex- 

 planation, like a magnetic awareness, a compass-like sense, a delicate per- 

 ception of the Coriolis force, or some other discrete sensory capacity by 

 which the geographic direction to home is perceived. This insistence on the 

 complete efficiency of one directive source is set forth by Huxley ( 1954 ) as 

 he dismisses the idea that birds may rely on the sun as a guide to their 

 travel. "There is," he says, "the hypothesis that pigeons navigate by the sun. 

 If they do, they must possess, built into their nervous systems, the equiva- 

 lents of a chronometer, a sextant, navigational tables and a calculating 

 machine for correlating the solar data observed at the point of release with 

 those at the loft. ... All in all, solar navigation seems just as untenable 

 as the canal theory or the magnetic theory." 



But neither Matthews nor Kramer claims the sun to be the sole factor 

 in orientation. Matthews (1955:98), after having discovered that his pi- 

 geons, gulls, and shearwaters had a direct homeward orientation when re- 

 leased at an unfamiliar place on a sunny day, and having shown that this 

 direct homeward orientation broke down when the sun was hidden behind 

 cloud overcast, demonstrated "that when Pigeons are very familiar with a 

 release point, after six previous releases there, overcast conditions have no 

 effect at all on initial orientation." In short, Matthews' work shows that ex- 

 perimental birds orientate directly homeward from strange regions with the 

 sun in view, are confused in strange regions with the sun hidden, but can 

 orientate homeward without the sun on familiar range. The sun may thus 

 play a role in the travels of birds as it does with men: if the way is familiar 

 by previous experience, the sun is not necessary to homeward orientation, 

 but if the way is not familiar, the sun is fundamental. 



Griffin ( 1952a, 1953 ) has described three types of homing, these apply- 

 ing to experimental birds set free by students of avian navigation and also 

 to free birds in the wild: 



Type I. Reliance on visual landmarks within familiar territory and the 

 use of exploration or some form of undirected wandering in unfamiliar ter- 

 ritory. 



Type II. The ability to fly in a particular direction, even in unfamiliar 

 territory. 



Type III. The ability to head for the home locality even when released 



194 



