BIRDS OF THE SOUTH ORKNEY ISLANDS 373 



Sterna hirundinacea, Lesson, South American Tern. 



The Scotia Expedition found this species breeding on Laurie Island to a total number 

 of from two to three hundred birds. During the visit of the ' Discovery II ' no nests of 

 terns were examined on Laurie Island, and only a few birds were seen, usually singly, 

 at sea round the coast. The localities in which they were found nesting by the Scotia 

 Expedition were not visited, but no doubt the birds still use these breeding places. 



Sterna vittata georgiae, Reichenow, Wreathed Tern. 



Both this bird and S. hirundinacea breed in the South Orkneys, and the Scotia 

 Expedition found that the terns breeding on Laurie Island were all of the latter species. 

 It is impossible to differentiate between the two birds by field observation alone during 

 the breeding season, and as only one tern was captured during the visit of the ' Discovery 

 II ', we were not able to identify the species inhabiting some of the colonies. I am of the 

 opinion, however, that most of the terns breeding in the group belong to the species 

 S. V. georgiae, with the exception of the Laurie Island birds, which were not closely 

 observed. 



A small ternery is established on the low islet forming the south-eastern boundary 

 of EUefsen Harbour. This was visited on January 5, and found to contain about fifty 

 nests. Most of these contained single hard-set eggs, and one newly hatched chick was 

 seen. The nests are shallow depressions in the rubble lying among the rocks, and are 

 lined with small pebbles. 



A number of terns were seen off Fredriksen Island and in Lewthwaite and Washing- 

 ton Straits. Along the north and west coasts of Coronation Island they appear to be 

 entirely absent, for these coasts provide no suitable nesting sites. Only three birds were 

 seen in Sandefjord Harbour during a stay of several days. 



Signy Island, however, provides breeding places for perhaps a thousand birds. Two 

 considerable colonies are established on the shores of Borge Bay, the nests being placed 

 high up on the beaches and on the rising ground at the back of them. All the nests 

 examined contained single eggs, and on January 16 these were all about half-set. Thus, 

 with this species again, the breeding dates on Signy Island are later than those of the 

 birds in EUefsen Harbour. A few patches of snow were still lying about the slopes of 

 the land in Borge Bay, and probably this more sheltered area would carry more snow 

 than would the comparatively wind-swept islets about EUefsen Harbour. Consequently 

 the EUefsen Harbour sites would be clear of snow earlier in the summer and this may 

 account for the difference in the breeding dates. 



The nests in the colonies in Borge Bay were found to be spread over a considerable 

 area of ground. Sometimes two or three nests might be placed within a few feet of one 

 another, but as a rule they were widely scattered. No birds, however, were found 

 nesting in complete isolation. 



Terns which breed in high latitudes are usually migratory, and it is probable that this 

 species is entirely absent from the South Orkneys during the winter. There appears to 

 be no record of its occurrence at the group during the winter months. 



