164 



DISCOVERY REPORTS 



Wilson (1907, p. 67) believed that the condition of paleness was due to weathering 

 of the plumage. In my opinion this is an error, due to the fact that the pale parts of the 

 feathers are much more susceptible to the effects of weathering than are those parts 

 which possess the darker pigments, brown and chestnut, as can easily be verified by 

 examination of skins. 



The number of specimens of the Brown Skua available for examination has been 

 substantially increased since the publication of the Birds of Australia by G. M. Mathews 

 in 191 3, and the purpose of this paper is an examination of the validity of four subspecies 

 named in that work. According to Lowe and Kinnear (1930) the following is the correct 

 nomenclature : 



Catharacta skua antarctica (Lesson), Falkland Islands, Tristan da Cunha and Gough 

 Island; 



C. s. clarkei (Mathews), South Shetlands, South Orkneys and South Georgia; 



C. s. intercedens (Mathews), Kerguelen and Crozets ; and 



C. s. Idnnbergi (Mathews) of the New Zealand region. 



These subspecies are supposed to be distinguishable by differences in plumage and 

 in the measurements of wing, tarsus and bill. 



In order to facilitate an examination of the data I have adopted a division into seven 

 geographical groups: 



PLUMAGE 



As a preliminary it should be said that field observations must be accepted with 

 reserve ; it is extremely difficult and often impossible to say if a bird seen on the wing 

 is large or small, pale or dark. Alterations in appearance due to background, movement 

 or light are usually too numerous and sudden to permit of them being taken into account : 

 it may be added that at a short distance at sea all brown skuas look dark, sometimes 

 almost black. 



The longest series of skins available for examination in the British Museum is that 

 from the Falkland Islands ; it contains thirty-seven specimens. Of these twenty-seven 



