258 BRITISH SEA BIRDS. 



egg. Both birds assist in making this burrow, 

 which often runs under some mass of rocks, and 

 many holes are begun and deserted for no apparent 

 reason, just as we find to be the case with the 

 Sand Martin and other hole-boring species. At the 

 entrance of all of the holes that are occupied there 

 is a considerable heap of droppings. Few, if any, 

 Shearwaters are astir even at a populous breeding- 

 station during the day ; all keep closely to their 

 burrows, remaining stolidly upon their nest until 

 dragged forth, struggling, into the light. Many 

 burrows are made close together, and in some cases 

 one main entrance will lead to several chambers, 

 each containing a nest. 



