174 DISCOVERY REPORTS 



fall within the limits of variation of the New Zealand race, although rather in the lower 

 part of the range of size. 



There is no advantage in dividing up the Brown Skuas into four subspecies of which 

 two are so ill defined that they cannot be identified except by reference to the localities 

 on the data labels; the validity of subspecies should depend on the possession of 

 intrinsic characters. It follows therefore that groups which cannot be differentiated 

 from the New Zealand race should be included with it in one subspecies. 



It is my opinion that the Brown Skua should be divided into two subspecies, a larger 

 and a smaller, which have a common meeting place in the South Shetlands. The names 

 and distribution are : C. s. antarctica (Lesson), of the Falkland Islands and the South 

 Shetlands, and C. s. lonnbergi (Mathews), of New Zealand, the Crozets, Kerguelen, 

 South Georgia, the South Orkneys, Tristan da Cunha, Gough Island and the South 

 Shetlands. C. s. clarkei (Mathews) and C. s. intercedens (Mathews) thus cease to exist, 

 part of the former and the whole of the latter being absorbed in C. s. lonnbergi and the 

 remainder of clarkei being included in C. s. antarctica. 



NOTE ON THE DISTRIBUTION OF McCORMICK'S SKUA 

 L. Gain (191 5) has stated that he found McCormick's Skua on Deception Island, 

 South Shetlands, where it was mixing with the Brown Skuas but was more numerous. 

 He found maccormicki nesting as far north as Admiralty Bay, 62 6' S, and mentions 

 it as nesting at Port Lockroy in Wiencke Island, 64 ° 49J' S. In the course of a number 

 of visits to the South Shetlands by Mr A. G. Bennett and myself no specimen of 

 maccormicki has been collected, and in my observation the whole area as far south as 65 

 of latitude is occupied by the darker bird, i.e. C. s. antarctica. 



The brown form is abundant and nests at Deception, and while Gain records having 

 seen it as far south as Wiencke Island at the south end of the Belgica Straits he states 

 that it did not nest in the Straits. In 1922, however, I found that Port Lockroy had 

 become a nesting site. 



It may be suggested that the Brown Skua, which is slightly larger than maccormicki, 

 favoured by the abundant food supply derived from the extensive whaling operations 

 subsequent to 1909, had succeeded in ousting maccormicki from its former breeding 

 places in the South Shetlands, at least as far south as Port Lockroy. It is well known 

 that the skuas are most combative birds and even given to cannibalism at times. 



LITERATURE 



Clarke, W. Eagle, 1915. On the Birds of the South Orkney Islands. Scottish National Antarctic Expedition, 

 IV, pp. 219-47. Edinburgh. 



Gain,L., 1915. Oiseaux Antarctiques . Deuxieme Expedition Antarctique Francaise, pp. 1-200, 15 pis. Paris. 



Lowe, P. R. and Kinnear, N. B., 1930. Birds. British Antarctic ('Terra Nova') Expedition. Nat. Hist., iv, 

 pt. 5, pp. 103-93, 16 pis. London. 



Mathews, G. M., 1913. Birds of Australia, 11, pt. 4. London. 



Wilson, E. A., 1907. Aves. National Antarctic Expedition. Nat. Hist., 11, pt. 2, pp. 1-121, 13 pis., 46 text- 

 figs. London. 



