SEA-BIRD MOVEMENTS I49 



of land and water from Lewis to South Uist. Wlien Thomas Pennant 

 travelled on his famous tours in Scotland he found arctic skuas nesting 

 on Islay and Jura in 1772; but they have bred since only sporadically 

 on these islands, e.g. on Jura in 1890 and 1939 and on Islay in 1922. 

 At least one pair bred regularly in Sutherland until the end of the last 

 century, but now it is sporadic there. It has nested sporadically also 

 in Tiree (1891), Argyll (c.1931) and West Inverness (1928-33). 



At sea the arctic skua has been called "the unfailing attendant of 

 the arctic tern," and follows this and other species across the equator 

 in both Atlantic and Pacific. The plot (Fig. 25, opposite) of at-sea records 

 in the North Atlantic, as compared with other ocean areas, reflects 

 the distribution of observers rather than that of skuas; but there is 

 no doubt that the arctic skua passes to its winter waters by ocean 

 passages. It reaches the Straits of Magellan by the Pacific and probably 

 also by the Atlantic, has been recorded from St. Paul Rocks and St. 

 Helena, and reaches the Cape in Africa. It is recorded from tropical 

 \Vest Africa, though it does not appear to concentrate around and south 

 of Cape Verde as does the pomarine skua. It passes along the U.S. 

 seaboard to the Mexican Gulf, North Cuba, the Bahamas and the 

 Sargasso Sea, and has been recorded from the Grenadines in the West 

 Indies. It passes commonly along both east and west British shores, 

 and to a certain extent also overland in Europe to the Mediterranean- 

 Caspian line; and some elements reach the southern Red Sea, the 

 Persian Gulf, and the Mexican coast. West Pacific birds reach New 

 Guinea, Australia, New Zealand and Chatham Island. 



The breeding-distribution of the long-tailed skua, Stercorarius 

 longicaudus is not the most restricted, but its at-sea distribution is the most 

 mysterious (Fig. 26 p. 150). Its population is much smaller than that 

 of the arctic skua, and probably smaller than that of the pomarine 

 skua. Its nesting distribution is wide through the arctic, but scattered 

 and over vast regions (see map) sporadic; it extends south of the 

 Arctic Circle to the Dovre Fjeld area, or even farther south in Norway. 

 It breeds south to Nunivak Island in Alaska, to York Factory^ in 

 Hudson's Bay, probably not to northern Labrador and Iceland; the 

 evidence is unsatisfactory from these areas. It does not breed in south 

 Greenland, or on Bear Island and many other arctic islands; in general 

 it nests only where there are small rodents available, particularly 

 lemmings, though it does not need these, for it has successfully nested 

 on Jan Mayen (once, in 1900) and several times in Spitsbergen (e.g. 

 1 931), where there are no rodents. One of us was stooped at by a 



