68 Mr. D. A. Bannennan on an Ornithological 



it was just possible to squeeze; after being pulled in front 

 and pushed behind for some fifteen yards, I at last found 

 myself in another small cave,- with yet another tunnel leading 

 out of it at right angles to the last. This second tunnel was 

 a little wider, but twisted and turned in the most bewildering 

 manner, gradually opening out into a good-sized cavern 

 which must have been quite twenty yards from the entrance. 

 All the large holes and crevices in the walls of this cave had 

 been utilised by the Shearwaters. A very large number 

 must resort to this particular spot. At this distance from 

 the fresh air an indescribable smell of Petrel greeted our 

 nostrils. The floors of both caves and passages, which were 

 composed of crushed lava, were thickly strewn with the 

 feathers of the birds, and I was unlucky in finding all the 

 occupants out at sea. They had not yet commenced to lay, 

 at any rate in this cave, but we had obtained a fair number 

 of eggs from other parts of the island. The fishermen said 

 that the birds had now come " to clean their nests. ^^ The 

 entrance to this lower cave must be three-quarters of a mile 

 from the sea ; and although, in the daytime, the birds 

 were often seen flying up and down the strait which sepa- 

 rates Graciosa from Lanzarote, yet they never by any chance 

 came to their nesting-holes before darkness had fallen. I 

 took considerable pains to discover what rule governed the 

 comings and goings of these Shearwaters between the sea 

 and their nesting-sites. Living, as I did, on Graciosa and 

 Montana Clara in their very midst, I hoped to be able to 

 arrive at some definite conclusion on this somewhat little 

 known subject ; with this object in view, I made many 

 journeys to different nesting-places after dark. Before lay- 

 ing had become general [i. e. during my stay on Graciosa), 

 the majority of the birds would leave their nests before it 

 became light, spending the entire day at sea. They must be 

 excellent time-keepers, for in many cases no inkling of day- 

 light could possibly reach them to warn them that the dawn 

 was breaking. Unless, therefore, they leave their holes before 

 daybreak^ while it is still dark, I do not believe that they 

 leave them until dusk, and possibly not until the following 



