NAVIGATION BY SEA-BIRDS 163 



the Equator and was recovered at Durban, Natal, on 30 October 1951 

 — average rate, about 100 miles a day for 114 days!), the individual 

 has presumably become acquainted with what is, to man, an almost 

 trackless route. As to the young non-breeding adult of over a year old 

 it will presumably have the older more experienced adults to travel 

 with. Rowan (1952) suggests that great shearwaters form rafts on the 

 sea close to the breeding islands at the end of the season in preparation 

 for departure in flocks for the northerly migration. But what of the 

 fledgeling of those species such as the petrels and the puffins, which is 

 deserted by its parents a week or two before it leaves the land, and 

 travels solitarily to the sea? It may be observed making its way alone 

 into the ocean up to fifty miles or so from the breeding-ground, as 

 we have ourselves recorded. What happens to it in the next few days 

 no one seems to have observed accurately, but it can receive no guid- 

 ance from the adults in those early weeks — they are far at sea, and in 

 moult. Probably, like the fledgeling gannet, it soon overtakes the 

 adult flocks or at least passes through their extended wintering range, 

 and, guided by an instinctive orientation, proceeds to a nursery or 

 wintering-ground of juveniles, perhaps hundreds of miles beyond 

 that of the adults. We would cite the case of a Manx shearwater, 

 ringed as a juvenile at Skokholm on 10 September 1951, which was 

 reported from Rio de Janeiro on 20 November 1951, thus confirming 

 what we had long suspected: that the Manx shearwaters which are 

 known to visit South America include young birds from Europe. 

 This particular juvenile had covered 5,050 nautical miles in a maximum 

 of 71 days (which is 71 miles a day), a striking performance for so 

 young a bird. Another ringed Manx shearwater has been recovered 

 in the South Atlantic; an adult marked on Skokholm in July 1947 

 reached a point 200 miles south of Buenos Aires in the autumn of 1952. 

 So the old shearwaters can migrate as far south as the young ones. 

 But the concentration of fulmars on the Newfoundland Banks, about 

 fifteen hundred miles from the nearest breeding station, may be a 

 young fulmar nursery. Fisher (1952) shows that the four marked birds 

 recovered there were all first year (juvenile) birds, two from Greenland 

 and two from St. Kilda. 



This must be a short chapter, because our knowledge of the mech- 

 anism of orientation is so limited. To sum up: it seems that sea-birds 

 may navigate like human beings do at sea. Although without mech- 

 anical aids, they find their way by learning the chart; by knowing 

 the time (it is becoming clear that most birds have an accurate time- 



