THE COASTAL TOPOGRAPHY OF ANTARCTICA 423 



THE COASTAL TOPOGRAPHY OF ANTARCTICA AND ITS INFLUENCE 



ON THE DEPLETION AND CONSERVATION OF 



THE SURFACE POPULATION 



In the northern part of the Falkland Islands Dependencies the ice-free areas of the Trinity Peninsula 

 and its adjacent large islands, with those of the South Shetland, South Orkney, South Sandwich 

 Islands and South Georgia, together provide innumerable coastal sites of suitable gradient where 

 krill-eating penguins. Ringed, Adelie and Gentoo, have established their rookeries on an enormous 

 scale. In the South Orkney group the naturahsts of the 'Scotia' (Bruce, 191 1) estimated that on 

 Ferrier Peninsula alone, one of the many promontories of the heavily sculptured coastline of Laurie 

 Island and a favourite site for Adelies, there were not less than two million birds. Brown (191 5 6) 

 adding that the Ringed population of Graptolite Island might run to several millions. As Murphy 

 (1928) once put it, the incredible numbers in which these social birds are encountered simply ' beggars 

 description '. From these estimates it would follow that over the whole area outlined above the rich 

 euphausian population of the western Weddell drift must suffer annually a major depletion from the 

 depredations of penguins alone. Severe, however, though their ravages m this locality unquestion- 

 ably must be it does not necessarily follow that penguins take a similar toll of the krill throughout 

 its whole geographical range. Long stretches of the coastline of continental Antarctica are occupied 

 by continuous vertical barrier ice cliffs on which these krill-eating birds, here exclusively Adelies,^ 

 even if they could gain a footing, would not choose to build. Suitable rookery sites, therefore, are not 

 only generally less concentrated in the East Wind than they are in the western part of the northern 

 zone but in certain parts of the former, notably throughout a vast section of the continental coast 

 reaching from Enderby Land to Vahsel Bay and beyond, are absent altogether, the barrier along this 

 particular stretch running for approximately 2000 miles not only unbroken by any rock, but free 

 throughout from offshore rocky islets on which the birds might establish their nests.^ Excellent 

 photographs of this ice-bound coast showing its gross unsuitabihty for congregating Adelies, and other 

 rock-frequenting birds, are given by Christensen (1938), Swithinbank (1957a, i957*). Gessner (1942) 

 and van Rooy (1957)- The persistence of fast ice occasionally thrusting far out to sea during the 

 breeding season could also it seems be a serious embarrassment to the nursing birds, their rookeries 

 from time to time (Law and Bechervaise, 1957) being cut off for such enormous distances from open 

 water by undispersed winter ice that the chicks starve to death by the hundred before their parents 

 can return with their food. In terms of consumption of Euphausia this would mean that, bird for 

 bird, the far southern adult population, wherever such adverse conditions occur, has fewer mouths 

 to feed than the corresponding population in lower latitudes. The long frontage of the Ross Barrier 

 presents another obstacle to the nesting birds and I think it extremely likely too that all along the 

 Pacific side, from Alexander Island westwards to the Bay of Whales, suitable breeding sites will prove 

 to be absent or at most exceeedingly rare.=^ Incidentally, these immense ice barriers, pushing their 

 fronts far out to sea (Law, 1952) into deep water, create in many places round Antarctica quast- 

 pelagic coasts along which true coast fishes, such as, for instance, are so numerous and take such heavy 



1 Apart from the Emperor, which is essentially a squid-eater, the Adelie is the only penguin frequenting the coasts of the 

 continental land beyond the Graham Land peninsula. It does not extend to the Subantarctic islands. Elton (1927, pi. vii) 

 publishes a photograph, from Mawson (1915), showing a vast congregation of birds with the legend 'Adelie penguin rookery 

 on Macquarie Island'. This is a rookery of Royal penguins. 



2 In a map just published Sladen (1958) shows this stretch of the coast without a single AdeUe breeding site. 



3 The latest American expedition to visit this sector reports none in the southern parts of the Bellingshausen and Amundsen 

 Seas (between 120° and 80° W), and that the birds themselves are exceedingly scarce, being represented as a rule by lone 

 individuals or at most by two at a time (Anon., 19606). 



