COMMON AND ARCTIC-TERNS 93 



being the young of the year. 1 Both species are harried by Skuas, 

 which pursue them and compel them to drop the fish they are 

 carrying. (PL 100.) 



Their eggs, in spite of their vigilance, are occasionally robbed by 

 Crows and Gulls, also by rats. In 1905, at Walney, hardly an egg of 

 the Arctic-tern escaped the last-mentioned marauders, traces of 

 whose feet and tails were to be seen leading from almost every nest to 

 the nearest tuft of bent, where the broken shell told the story of the 

 theft. The deep narrow furrow made in each case by the tail in the 

 sand seemed to show that the rat had used this appendage as a 

 support while it hopped away on its hind-legs, clasping the egg to its 

 breast. That it escaped being murdered by the terns is remarkable. 

 Where sheep and cattle have access to the breeding-ground, some 

 eggs are, of course, trodden upon. Some again, as previously noted, 

 are washed away by the tides from nests laid on or below high-water 

 mark. 



The unfledged young suffer, no doubt, chiefly from rain and 

 cold. Those of the common-tern, born on river banks, are also liable 

 to be drowned by floods. 2 From birds of prey they appear to be well 

 protected by their protective coloration, when this assimilates with 

 their nesting-ground, and by the watchfulness of the parent birds, 

 which also, no doubt, serves to guard them from creatures that hunt 

 by scent. But with regard to this information is lacking. 



The Arctic and common-terns both begin to leave their breeding- 

 places in August. Of the manner of their departure little is recorded 

 by British observers, but Mr. G. H. Mackay has given some interesting 

 details of the proceedings of the common-terns in 1895, before they 

 left Muskeget Island, off the New England coast. From September 

 1st to 7th they appeared to leave the middle of the Island, and 

 roosted on the outside beaches on the west and south. From the 15th 

 to the 22nd they were seen collecting in large flocks, mounting 

 upwards in a spiral course, then descending again. On the 26th and 



1 Cf. Nauraann, Vogel Mitteleuropas, xi. 135, 146. 2 Naumann, op. tit., p. 146. 



