370 DISCOVERY REPORTS 



leads one to suspect that the egg was a well-preserved unhatched specimen from the 

 previous season, for among the southern petrels it is uncommon to find both birds of a 

 pair at the nest after the egg is laid. 



In the course of our work two nests were found in crannies among rocks on the 

 steep slopes of the eastern side of Wilton Bay, at a height of about 150 feet. In both 

 these the egg was fresh, not laid more than a few days, and a single parent was present 

 in each case. This was on January 28, so that the egg-laying dates must coincide closely 

 with those of O. oceaniciis. One of the sitting birds was captured and preserved. The 

 bill, legs and feet are all black, and the iris very dark brown. 



Bennett (1926) comments on a peculiar whistling note which he believes this bird to 

 utter in the neighbourhood of its nest. Eagle Clarke also mentions a whistling from the 

 nest. This habit is not, however, confined to this species, for Wilson's Petrels are often 

 heard to make similar sounds. 



The two birds seem to be very similar in their habits, with one notable exception. 

 Wilson's Petrels nearly always follow in the wake of a ship at sea, while Fregetta tropica 

 melanogaster is usually seen flying ahead of or around a ship and rarely follows the 

 wake. It also appears to be a much more agile bird on the wing, and the following note 

 was made on birds observed at sea between the South Orkneys and South Shetlands : 

 " The flight of these birds was again seen to be most distinctive. They fly rapidly along 

 about four feet above the surface of the sea, and at intervals make a series of short, 

 oblique dashes down to it, striking it with the feet held out and ' skating ' for a distance 

 of three or four feet, raising a considerable splash." 



The birds are moderately common in the high latitudes of the South Atlantic in 

 summer; and in the Drake Strait, Scotia Sea, and the vicinity of the South Orkneys 

 and South Shetlands, small numbers are recorded as having been observed on almost 

 every day that the ' Discovery II ' was at sea. In the winter they probably migrate to 

 lower latitudes. 



Bennett found this bird breeding in small numbers on Deception Island, and it is 

 probable that the eastern islands of the South Shetlands also furnish breeding grounds. 



Catharacta skua lonnbergi, Matthews, Brown Skua. 



A great deal of confusion has prevailed with regard to the subspecific races of the 

 Great Skua, and in recent years the southern skuas have received considerable attention. 

 The latest analysis by Hamilton (1934) is an important contribution to the subject. 

 A long series of the measurements of mated pairs, from the South Shetlands and South 

 Orkneys, is required to confirm his conclusions. This might prove that the birds of 

 Hamilton's two subspecies interbreed, in which case the subspecific characteristics are 

 no longer valid. On the other hand, if the opposite were proven his case is beyond 

 question. It may be noted that Bennett (1926, p. 319) states that in the South Shetlands 

 he observed that breeding pairs were alike in size. 



Hamilton was only able to measure thirteen specimens from the South Orkneys, 

 twelve from the South Shetlands, and nine from South Georgia, and he remarks on the 



