60-- 



Zocka/l 



IV 12' If 10' 9° 6' 7* 6* 5° 4' 3* 2* 1' O' 



■_L I 1 1 T I I : I \ I I I I 



r^ 



1' 2' 



lOOKM 12 



MI LES 



11 



km: 



4 16-9 (-) 5 



29-4 (+)• 71^ 23-5 





t5-3W: 



WLONG. 9 



-12 



1 E LONG 



Fig ga 



The principal breeding-colonies of the common guillemot in Britain. The percentages 

 of bridled forms in the breeding-populations, as determined chiefly by H. N. Southern 

 and his colleagues, are shown. Minus and plus signs in brackets indicate changes in 

 the decade c. 1939-t. 1949 which are significant, or on the borderline of significance. 

 Crossed circles mark sites of former colonies. 



