352 DISCOVERY REPORTS 



SYSTEMATIC ACCOUNT 



Aptenodytes forsteri, G. R. Gray, Emperor Penguin. 



The Emperor Penguin occurs at the South Orkneys only as an occasional winter 

 straggler. According to Mr Bruhns, the official in charge of the Argentine Meteoro- 

 logical Station in Scotia Bay, one or two birds are seen during the course of nearly every 

 winter. From his description these are mainly aduhs. They only occur when the islands 

 are closely surrounded with pack-ice and are evidently non-breeding birds. In the 

 summer, the bird has apparently not recently been seen at the station, though the islands 

 are often beset with ice for periods during the summer. 



The Scotia Expedition have a record of a bird, probably belonging to this species, 

 which was seen in Scotia Bay in November 1903, and two were seen in March 1905 

 (Eagle Clarke, 1906). 



Emperor Penguins are comparatively common in the ice of the Weddell Sea, and it 

 is probable that there is a fairly extensive breeding ground somewhere within its area. 

 The birds which occur at the South Orkneys are certainly from the Weddell Sea, and 

 travel up on the great ice drift from its western side. In January 1932, several adult 

 birds were seen in pack-ice about 250 miles east-south-east from the Orkneys, but in 

 1933, when the ' Discovery II ' visited the group, there was no pack-ice in the vicinity. 

 Since the Emperor Penguin is essentially a bird of the pack-ice, it would never be seen 

 in the South Orkneys when open sea surrounds them. 



Pygoscelis adeliae (Hombr. et Jacq.), Adelie Penguin. (Plate XI, fig. i.) 



Adelie Penguins are extremely numerous in the South Orkneys, and a rough census 

 taken of all the rookeries in the group resulted in a total of about 1,500,000 nests. This 

 gives a population of about three million. The Scotia Expedition estimated the number 

 at five million (Eagle Clarke, 1906), but it is difficult to estimate the number with any 

 degree of accuracy. There was no evidence either of increase or decrease in the number 

 of nests in the rookeries, and the inference is that the penguin population maintains 

 a fairly even level. At a rough estimate, perhaps half the chicks hatched (about 

 1,500,000 birds), take the water for the first time each year. Apparently little is known 

 of the normal span of life of penguins, but the mortality rate, even among adults, must 

 be high. Probably in the winter months, as well as in the breeding season, many fall 

 victims to sea-leopards, killer whales, and natural catastrophes. It is doubtful if many 

 perish from starvation, for there is always food in plenty, and the only circumstance 

 which would be likely to involve risk of starvation would be for parties of birds to be 

 stranded on unbroken fields of consolidated pack. This, in the Weddell Sea area where 

 the ice is always moving, would be of rare occurrence. 



Laurie Island is the chief breeding-place for the birds, and huge rookeries are 

 established on every suitable site. On Weddell and Saddle Islands the majority of birds 

 are P. antarctica, for here the sites are generally steeper. On Powell Island there are 

 large rookeries, but on Coronation and Signy Islands there are only five comparatively 

 small rookeries in all, none of which are to the west of Signy Island. Thus in the South 



