348 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 9 



island. We can take it that the shearwater has an eye well adapted 

 for nocturnal work, but I do not think that the power of its eye can 

 account entirely for the ease with which it picks out the entrance to 

 its burrow in a crowded warren on a dark night, and the ease with 

 which, having alighted beside the entrance, it finds its way in the dark 

 labyrinth underground to its particular nesting recess. There is 

 some other power there, probably not unconnected with its wonderful 

 sense of orientation. 



I have seen sea birds such as puffins, razorbills, and shearwaters 

 flying confidently through thick mist in the direction of their breed- 

 ing grounds when I only knew that direction by a study of the 

 compass. How is this done? How, indeed, does another shear- 

 water, the great shearwater which winters in the North Atlantic 

 during our summer, find its way back to its breeding ground in the 

 Tristan da Cunha group of islands, a group which is but a needle in 

 the haystack of the South Atlantic Ocean ? If we knew the answer, 

 we should know the mechanism of the bird's power of orientation. 

 One worker. Dr. Riviere, has called this power "a sense of geograph- 

 ical position" (5). Dr. Riviere was working with homing pigeons 

 flying over land or within sight of land. But the sea bird may be 

 out of sight of land for days on end. Moreover, it does not usually 

 fly high like a pigeon ; more usually it skims the tops of the waves, so 

 that its horizon must be very limited. 



We have conducted some experiments with ringed sea birds in an 

 attempt to learn something more of this homing power (6). I can- 

 not give tonight more than a short sketch of the more important re- 

 sults. An adult shearwater was taken from its egg on Skokholm 

 and released at Start Point, in Devon, which is about 220 miles from 

 the island by the sea route around Cornwall, or 125 miles overland 

 as the crow flies. When released it flew low over the waves making 

 for sea. It did not attempt to rise up and strike overland in a bee- 

 line for the island. Yet that bird was back on its egg at Skokholm 

 within 10 hours, so that if it continued by the sea route it must have 

 flown steadily at 22 miles per hour. Of course its speed by this sea 

 route must have been much greater, since a shearwater normally does 

 not travel in a straight line but has a curved deviating flight, and 

 probably it paused to drink if not to feed. 



Two birds released at Frensham Pond, Surrey, performed a simi- 

 lar feat and were back at their nests the following night, but in this 

 case, before reaching the sea after release, these birds had to cross 

 40 miles of land. But land masses interposed between shearwaters 

 and the sea do not seem to disturb the homing faculty. Shearwaters 

 released at Birmingham, Evesham, and Manchester, as well as at 

 Limerick, in Eire, have safely homed to Skokholm, though not with 



