THE OLDER STAGES 151 



In daylight the presence of patches is often betrayed by large, sometimes enormous, congregations 

 of birds. In one region of patchiness encountered off the south-eastern tip of South Georgia in 

 February 1931 Gunther records a 'vast gathering' estimated to total some 5000 birds which in flocks 

 of from 200 to 300 was spread over an area of about one square mile. It consisted mainly of Whale 

 Birds, ^ but included numbers of Wandering Albatrosses, Black-browed Albatrosses, Cape Pigeons 

 and the South Georgian Diving Petrel, Pelecanoides georgicus Murphy and Harper. Among other such 

 gatherings Gunther notes the Sooty Albatross, Wilson's Petrel, Silver Grey Petrel, Antarctic Petrel 

 and Snow Petrel, all the species just mentioned it will be seen, with the exception of the unidentified 

 Whale Bird (or Birds) and the Diving Petrel, being recorded in the list of krill-eaters given on p. 128. 

 Bruce (191 5) vividly describes a triple association of krill, birds and whales, 'myriads of Cape 

 Pigeons and thousands of finners ', he saw between the South Shetland and South Orkney Islands in 

 December 1892. 



The sight of these whales and birds . . . will for ever remain one of the most vivid of my Antarctic recollections. 

 Whales' backs and blasts were seen at close intervals quite near to the ship, and from horizon to horizon, while 

 Cape pigeons were tumbling over each other after small pieces of fat thrown over the ship's side, just as do fulmar 

 petrels after scraps of whale fat in the northern hemisphere. These Cape pigeons were captured with an ordinary 

 hand landing-net over the side of the ship in such numbers that our crew of forty-seven hands were furnished with 

 a very full supply of 'sconce'. The sea was swarming with Euphausia. 



Matthews (1951) also refers to the vast numbers of birds that congregate to feast on the surface 

 patches : 



As far as we could see in every direction the sea was covered with birds, mostly White mollies, sitting close together 

 and all facing the breeze. Here and there among them were smaller flocks of Blue mollies and Wanderers, and the 

 spaces were filled with immense numbers of smaller birds. Cape Pigeons and Shoemakers, while over all skimmed 

 great flocks of little dove-grey Whale-birds, probably hundreds of thousands, their wings flashing as all the birds in 

 a flock turned together like sandpipers over an autumn mud-flat. 



Almost identical congregations are mentioned by Cook (1777) and Forster (1777) vA\o note par- 

 ticularly the vast numbers of ' blue peterels ' (Whale Birds) they saw as their vessels were approaching 

 South Georgia. 



Discoloration of the sea by patches leads one to suppose that the individuals of a patch are so 

 densely crowded that they must practically be jostling one another, close-range observation distinctly 

 suggesting they are. In some notes he made on a patch seen in particularly clear water near South 

 Georgia in January 1931, Gunther describes the krill as being densely packed in close formation and 

 all headed in the same direction parallel to one another. Each animal was distinctly separated from 

 its neighbour by an average distance of about two-thirds of an inch, although heads and tails 

 were often overlapping. At the beginning of his description quoted on p. 154 Hardy provides us 

 with another instance of how densely crowded they must be. 'For a whole day', he writes, 'there 

 was a dense swarm, like a red cloud, of closely packed euphausians {Euphausia superbd) against the 

 jetty at our shore station. There must have been thousands and thousands in a close swarm some four 

 feet across'. These observations, particularly Gunther's, suggest a density that might well be of the 

 order of at least one euphausian to the cubic inch. It is interesting, therefore, to record that in a 

 photograph recently taken from a bathyscaphe, 610 m. down, Peres (195 8) shows unidentified swarming 

 euphausians, ' Nuages d' Euphaiisiacea au voisinage du fond ', that might well it seems be packed as 

 tightly as this. Moore's observations on the swarming of a species that was evidently (p. 137) either 

 Thysanoessa inermis or Meganyctiphanes norvegica distinctly suggest a density of the same high order. 

 Similar concentrations have been reported for other swarming plankton animals, VanhoflFen (1902), 



1 Most probably f Matthews, 19296) Banks' Whale Bird, Prion banksi Gould, or possibly Prion desolatus Gmel., or both. 



