STRUCTURE AND SEA-BIRDS OF THE N. ATLANTIC I7 



tubenoses and has no gannets, shags, kittiwakes or puffins. The 

 long-tailed skua has a somewhat specialised breeding distribution in 

 Lapland, mostly inland. The remaining birds of this temperate 

 stretch of the east Atlantic breed from Britain, the North Sea or the 

 Baltic south beyond its limits; they are the roseate, little and Sand- 

 wich terns. Britain is the European headquarters of the roseate tern. 



About half the members of this east and north Atlantic temperate 

 sea-bird community are truly oceanic; that is, they may be found in 

 mid-ocean, up to the greatest possible distance from land, wherever 

 there are suitable feeding waters. Storm-petrels, Leach's petrels and 

 fulmars are the oceanic tubenoses of this community, and we now 

 find that the Manx shearwater also has a right to be considered 

 oceanic. Among the auks the dovekie and Briinnich's guillemot from 

 the north join the puffins, razorbills and guillemots in ocean wander- 

 ings. Here, too, are found all the four skuas of the northern hemisphere 

 and one, but only one, gull — the highly specialised kittiwake. In the 

 waters a hundred fathoms deep or less, that is, on the so-called conti- 

 nental shelf, we find all the birds previously mentioned, together with 

 the gannet, the black guillemot, and gulls of the genus Larus — the 

 great blackback, the lesser blackback and the herring-gull. Once we 

 are within sight of shore quite a number of species are added to our 

 list, and the tubenoses, except for the Manx shearwater and fulmar, 

 drop out. Here are the terns, the black-headed and common gulls, 

 and also the cormorant and shag, the one haunting mostly seas in 

 sight of sandy shores, and other seas in sight of rocks. 



By far the most impressive of the sea-bird haunts are the breeding 

 cliffs, where the different species are zoned vertically as well as hori- 

 zontally. Whether the rocks be volcanic or intrusive or extrusive or 

 sedimentary, we are sure to find Larus gulls breeding on the more 

 level ground a little way back from the tops of the cliffs — fulmars on 

 the steeply sloping turf and among the broken rocks at the cliff edge, 

 puffins with their burrows honeycombing the soil wherever this is 

 exposed at the edge of a cliff or a cliff buttress, Manx shearwaters or 

 Leach's petrels in long burrows, storm-petrels in short burrows and 

 rock-crevices, razorbills in cracks and crannies and on sheltered 

 ledges, guillemots on the more open ledges where they can stand; 

 perhaps gannets on broad flat ledges or on the flattish tops of inacces- 

 sible stacks, cormorants with their nests in orderly rows along broad 

 continuous ledges, shags in shadowy pockets and small caves and 

 hollowed-out ledges dotted about the cliff, kittiwakes on tiny steps 



