364 DISCOVERY REPORTS 



sound of a watchman's rattle. This note was sometimes heard on other occasions when 

 birds were flying close to the ship at sea, and it appears to be a scolding note. They 

 were also heard to utter a quiet twittering, and on returning to their chicks made soft 

 clucking sounds. The Snowy Petrel has thus a more extensive vocabulary than most of 

 its relations. 



On January 8 several nests in Sandefjord Harbour were visited. Of these all but one 

 contained chicks, and in the exception the chick was just hatching. 



In all, about fifty nests were examined throughout the South Orkneys, and all the 

 Snowy Petrels seen apparently belonged to the one species Pagodroma nivea. Several 

 sitting birds were measured, and it was found that the measurements were fairly regular. 

 Almost certainly no larger birds were seen. Probably P. confusa is confined to the Ross 

 Sea area, if indeed it is a distinct species. 



Measurements of two nesting birds in Borge Bay were : 



The bill is black, the iris very dark brown, almost black. The plumage is entirely 

 white, except for a few small filaments of feathers just before the eye, which are bluish 

 black. Often when the birds are seen flying it appears certain that there is a patch of 

 grey pigmentation about the under wing-coverts. All the captured birds were examined 

 but no trace of it was found, and it seems that the grey appearance must be an illusion 

 due to shadow. The legs and feet are dark bluish grey, darker on the toes and claws. 



Priocella antarctica (Stephens), Silver-grey Petrel. (Plate XI, fig. 2.) 



The Silver-grey Petrel has for some years been suspected of breeding in the South 

 Orkneys, but nests had not apparently been found there before the visit of the 

 'Discovery II'. 



The bird breeds in large numbers round the south-western and north-western 

 corners of Coronation Island, where it was estimated that 25,000 nests are established. 

 The nesting grounds seem to be entirely confined to this end of the main group of 

 islands, for although a sharp look-out was kept, nowhere else was there any sign of 

 their breeding. 



The Inaccessible Islands are, however, the main stronghold of the species. The 

 northern cliffs of all three islands were, on January 25, seen to be dotted with nesting 

 birds from top to bottom, the total number of nests being estimated at not less than 

 half a million. The birds were apparently the only petrels breeding on these islands. 

 On Middle Island, a rookery of Ringed Penguins is established on a steep bluff, and 

 nests of the Silver-grey Petrels were scattered among the penguins. 



The only previous occasions on which this species has been found nesting was by 

 Nordenskjold's Swedish Expedition, who found the birds breeding on Cape Roque- 



