SEA-BIRD MOVEMENTS I35 



This most helpful piece of work has been widely accepted throughout 

 the ornithological world and there is no doubt that we are beginning 

 to understand the distribution of birds in these waters, and beginning 

 to see that the hidden topography of the sea^ which we have analysed 

 in our first chapter, is reflected in the distribution of sea-birds, which 

 has, for most species, a well-marked pattern, with seasonal changes 

 of an orderly kind. A recent important follow-up to Wynne-Edwards's 

 pioneer work on the distribution of sea-birds at sea, is the paper by 

 Rankin and Duffey, published in 1948, based on many transects made 

 by them when they were on operational duties in the Royal Navy 

 during the last world war. A pioneer investigator of the sea distribu- 

 tion of the North Atlantic sea-birds was the late Poul Jespersen (1924, 

 1929, 1930) whose excursions were further into the tropics than those 

 of other workers. It is now possible to make preliminary analyses and 

 maps as a result of these and other investigations which show not so 

 much a fortuitous distribution of observers as a real distribution 

 of the observed. Derived from all the available literature, and from 

 certain unpublished notes of Eric Duffey, one of us has made six maps 

 showing the distribution of the fulmar at sea on a two-monthly basis. 

 Every observation of at least one certain fulmar was plotted as accur- 

 ately as possible. The result (Fisher, 1952) shows not only the distribu- 

 tion of the fulmar through the seasons but the amount of information 

 on a sea-bird that is now generally available. 



While nearly all the inshore sea-birds are either resident or migrat- 

 ory it seems necessary that the word "dispersive" should be used to 

 describe at least some of the offshore and most of the pelagic species. 

 This word is not a contradiction of the word "migratory," because 

 many species are undoubtedly both dispersive and migratory, if we 

 use migratory to mean "making a regular journey in a particular 

 direction," and dispersive to mean "scattering in no particular 

 direction." In the early days of marine ornithology the word dispersive 

 was applied to many species. Quite early in the present century, 

 when the ringing recoveries of the guillemots began to mount up, it 

 became clear that a large number of British breeding birds made 

 northward journeys at the end of their breeding season, often north- 

 eastwards to the coast of Norway, instead of the expected southward 

 journeys. It was discovered, too, that even the inshore coastal terns, 

 particularly the young, sometimes made northward journeys, the 

 first journeys of their lives. Gannets, too, were found by ringing returns 

 to go north, south, east and west of their gannetries. It was thought 



