802 EXHIBITION OF LANTERN-SLIDES OF BRITISH TERNS. [JSTov. 23, 



association with the Common rather than with the Arctic Terns 

 although individually the pairs of Roseate Terns seemed to select 

 more isolated and somewhat concealed nesting sites than any 

 other species. Four of the eggs found he had carefully measured 

 and found the largest to be l^-J inches long and the smallest 11^. 

 On July 3rd, 1908, the last day of his visit, none of the Roseate 

 Terns or Common Terns in this area had hatched out, but quitt^ 

 a number of young Arctic Terns were found in the nests, some of 

 which were photographed. He found it rather difficult to 

 understand the statement of Dr. Louis Bureau with regaid to the 

 date of departure of this species (see report of the Ornithological 

 Congress held in London 1905) : — 



" The Roseate Tern arrived on the coast (of France) 



about the 15th of May, commenced nesting about the 5th of 



June, and departed on the 10th of July approximately." 



He hardly thought it possible for the young Roseate Terns to 



leave their nesting islands within say a fortnight of being hatched, 



and if Dr. Bureau's statement were to be accepted, it could only 



mean that the old birds departed, leaving their nestlings in an 



almost helpless condition. 



Arctic Tern {Stetma macrura). — He estimated that there were 

 10,000 pairs of this species on the nesting area, which was pro- 

 bably one of the largest colonies in the British Isles. They evinced 

 a marked preference for nesting just where the grassy portions of 

 the island intermingled with ridges and areas of bare rock. For 

 instance, he had marked out an area roughly rectangular in form, 

 140 yards long by 30 yards across. On each of the long sides of 

 this area a ridge of bare rocks protruded through the grass, and 

 walking along each of these two rocky ridges and finally walking 

 down the central liiie of the grassy area, he had noticed nests of 

 the Arctic Terns as follows : — 



Along Eastern rock ridge 

 „ Western ,, „ 



Total 



Along the central line of the grassy area there were 34 nests with 

 62 eggs. 



Again he had found extraordinary differences both in the sites 

 chosen for nests and in the materials of which the nests were 

 made, and a type series of such nesting sites and materials was 

 well shown in the photographs. A series of very beautiful slides 

 showing the Arctic Terns alighting at their nests with extended 

 wings was also shown. He had noticed that the Arctic Terns 

 were not only more vocal, but bolder and more vicious than any 

 of the other species. They would not only swoop at a passer-by 

 but would in many instances actually strike him as well. He 

 had noticed that both sexes shared in the duties of incubation. 

 The first young bird was hatched out on June 29th and on 

 July 1st he counted thirteen young ones, although this number 

 was by no means exhaustive. 



