96 THE TERNS 



question is the preference shown by this species for recesses in the 

 rocks as breeding-places. Heavy thunder showers will fill these 

 hollows with water, and I have not the slightest doubt that many eggs 

 are chilled and rendered infertile by this means. In this case the 

 skin and egg collectors cannot justly be held responsible for the 

 diminution of the species : a few have no doubt been shot from 

 various colonies, but the thorough identification of eggs in a crowded 

 colony is a work of time and patience, and the number of authentic 

 eggs in collections from the British Isles is very small. 



The roseate-tern arrives at its breeding-grounds after the common 

 and Arctic-terns, and does not appear till the very end of April. 

 Although nests may be found within a foot of those of one of the other 

 species, the roseate-terns tend to breed apart from their neighbours 

 and close to one another. In a colony where all three species were 

 nesting, Mr. W. Bickerton noticed a preference for association with 

 the common rather than the Arctic-terns, while in the main colony the 

 island is divided between common and roseate-terns, and only a few 

 Arctic-terns breed on outlying rocks. On the Fames, however, Mr. 

 Kirkman noticed a pair in 1909 standing on the ground among the 

 Arctic-terns, and this was also the experience of Messrs. Cummings 

 and Oldham on the Skerries. A very different state of things is 

 apparent, however, on visiting the great stronghold of this species in 

 the British Isles. From afar off the bold rocky island stands out 

 black from the sea, but its top is white with a snowy cloud of terns, 

 and even half a mile off the din of their creaking notes comes to us 

 across the waters. As the boat is steadily rowed towards the island, 

 the terns rise in hundreds and fill the air above us, until the rock is 

 deserted and every one of its tenants is on the wing. It is by no 

 means easy to estimate their numbers under these circumstances, but 

 probably from three to four hundred birds at least are flying over- 

 head, uttering an incessant chorus of creaking notes. There is not 

 the least difficulty in distinguishing the roseate from the common as 

 they fly overhead. The former is really a smaller bird, but, on the 



