THE SEA BIRD — LOCKLEY 351 



wild flowers form a natural garden of great beauty about the boulders 

 and crevices under and in which the razorbill lays its single egg. 

 But the individual razorbill has not been the easiest bird to study, for 

 it has the annoying habit of wearing out its ring on the sharp sand- 

 stone rocks of Skokholm, owing to its method of walking with its 

 tarsus close to the ground. For this reason practically all our earlier 

 records of individuals have been lost, the numbers on the rings having 

 been obliterated in a single year, and in 2 years the rings were worn 

 through and dropped off. Stronger rings are now being made, and 

 by giving the birds a new ring every year in place of the old, we are 

 keeping track of some promising individuals who have returned 

 to the same crevice year after year. In the winter individual razor- 

 bills have been recovered as far north as Norway and as far south 

 as the Gulf of Genoa, Italy. 



The guillemot, Uria aalge albionis (With.), breeds on less accessible 

 rock ledges, but we are keeping account of such individuals as we have 

 been able to capture here, and we try to ring all the young guillemots 

 just before they fly. 



The gannet, Sula hassana (L.), does not actually breed on Skokholm 

 but on the neighboring islet of Grassholm, which is the only site of 

 this species in England and Wales, and one of the most important of 

 the 20 colonies known to exist in the world. On Grassholm there 

 are today approximately 6,000 pairs of gannets. Since 1933 we have 

 ringed large numbers of gannets there in most summers. An analysis 

 of the returns from this marking suggests a very interesting migra- 

 tion. In their first winter the young gannets go a long way south, 

 several individual young birds from Grassholm having been recovered 

 off the coast of West Africa in latitude 20°]Sr. Gannets in their sec- 

 ond and third years, however, do not seem to travel so far south. 

 At least we have no records of Grassholm gannets of this age farther 

 south than the Straits of Gibraltar and the coast of Algeria, at Oran. 

 While older birds, gannets in and past their fourth year, remain 

 nearer home, no ringed gannets of this age have been recovered farther 

 south than the most northerly comer of the coast of Portugal. 



While it is never safe to dogmatize from these records, we can 

 suggest that, as the gannet reaches a mature state of plumage and 

 breeding condition in and after its fourth year, it may be disinclined 

 to wander far from its breeding site. This is to some extent con- 

 firmed by the fact that adult gannets assemble at Grassholm as early 

 as February, and they do not leave until the end of October or the 

 beginning of November. 



We have on Grassholm at the moment some individual adult gan- 

 nets which have nested there 3 and 4 years in succession. If the gannet 

 does not breed until 4 years old, these individuals must be 7 and 8 



