EVOLUTION 49 



3.2 in ten years; and at Unst in Shetland — 23.8 to 16.9 per cent, in the 

 same period. There has also been a significant decrease — of about 

 one-third — in Iceland; thus at Grlmsey in the north, from 8.7 in 

 1939 to 6.9 per cent, in 1949; at Hafnaberg, in south-west Iceland, 

 from 29 per cent, in 1939 to 18.1 per cent, in 1949; in the Westmann 

 Islands a parallel decline from 75 per cent, in 1935 (Lockley, 1936) 

 to 50 per cent, in 1949. 



Increases noted in the 1939- 1949 enquiries were several, but only 

 one, at Foula in Shetland, was significant and by checked observers 

 (from 24 per cent, in 1938 to 29.4 per cent, in 1948-49). Increases 

 on the margin of significance were recorded from St. Bee's Head in 

 Cumberland, Marwick Head in Orkney, and the Fair Isle. Apart 

 from these small increases in the last decade, there was a significant 

 increase of the percentage on Noss in Shetland from 15.5 in 1890 

 to 26.5 in 1938, which seems great enough to embrace a possible slight 

 observer-error. 



Unfortunately, too few of the early bridled guillemot counts are 

 reliable, though some from Berneray and Mingulay ('Barra Head') 

 in the Outer Hebrides may be so. This had 20.2 per cent, in 1871; 

 12 in 1939; 9.8 in 1949; 12.6 in 1950. The decrease between 1871 

 and 1939 is significant, though the other apparent changes are not so. 

 Elsewhere we have followed Southern in discarding such vague 

 records as 'about one in every nine or ten.' 



Nothing is yet known about the percentage of bridled guillemots 

 along the coast ofNorway, except that it has remained slightly over 

 50 per cent., at Bear Island from 1932 to 1948. At the Karlov Islands 

 off the Murmansk coast the percentage was 42 in 1938. It seems 

 likely, from the rather scanty figures from Novaya Zemlya, which 

 Southern slightly misdates and misplaces, that the percentage may 

 be about the same on islets in Pukhovy and Bezymiannaya Bays oflf 

 that island (36.4 and 50). 



These changes are curious and it is clear that much remains to 

 be solved about this interesting problem in distribution and evolution. 

 Nor is much known about the distribution of the bridled form in the 

 New World, save the following: H. F. Lewis found 128 bridled out of 

 a sample of 724 (17.7 per cent.) in the colonies along Quebec Labrador 

 in 1929. One of us found 51 bridled out of a sample of 295 (17.3 per 

 cent.) at Cape St. Mary, on the south-west corner of the Avalon 

 Peninsula of Newfoundland, in 1953. In June, 1940 at Funk Island 

 and other parts of the east coast of Newfoundland within forty miles 



E 



