AWARENESS OF DIRECTION 



sunlight with mirrors and by an artificial sun; and it was demonstrated that 

 with the sun obscured, as by overcast of cloud, the cage movements were 

 random, without directional bias. Kramer's Starlings were not merely aware 

 of the sun as division between night and day, nor simply as the cue to east 

 and west, morning and evening. These experimental birds related their 

 position to the sun in both time and space as it moved in its arc across 

 the sky. 



So convincing are Kramer's experiments that we must conclude that 

 wild birds, like his caged Starlings, perceive the sun as a cue to direction. 

 Santschi (1923) has shown how the sun is used as a compass by ants, and 

 in a wonderful little book Von Frisch (1950) tells us of the role of the 

 sun in the orientation of bees. Ants, bees, birds, and men perceive the sun 

 only as an accessory guide when traveling about their homes; but when 

 they are following a course beyond the limits of familiar surroundings, the 

 sun becomes a primary cue to direction. 



In the absence of the sun or of landmarks, as in overseas passages, the 

 texture of the water may serve as a cue to direction. Because of their 

 great inertia, waves may continue in a certain direction long after the wind 

 has changed. "Once the flight direction relative to this rather long-lived 

 system of parallel lines is established (from the bearing provided by the 

 sun, or by some other means), it is possible to use them over a period of 

 many hours as an indicator of direction." * Clouds may serve as a cue to 

 direction, either by their texture overhead or on the horizon where cloud 

 caps show above islands or mountain peaks. Flying above cloud, birds 

 may perceive their velocity and wind drift relative to cloud texture, but 

 of course they must become displaced over the land to the extent of the 

 cloud movement. 



Hitchcock (1950, 1952) has succeeded in training pigeons to fly in cer- 

 tain directions, which were followed by some of his trained birds when 

 released in strange territory. Kramer observed that, besides maintaining 

 their standard migrational direction in captivity, his Starlings could be 

 trained to move in certain ways. This suggests not only a retentiveness for 

 direction, but that such awareness may develop from a learning process. 



The ability to hold a course accounts for the migration of waterfowl 

 along standard directions during periods of heavy overcast. But the gyra- 

 tions of travelers over Delta during unfavorable weather suggests that they 

 seek some cue to direction to continue with a movement under adverse condi- 



• Robert L. Lillestrand, "The Flight of Birds in the Wind" (unpublished manuscript). 



197 



