::Photo Gallery:: picofmonthNov99

Bridled guillemots (murres) were once thought to be a separate species - the "tearful guillemot", Uria lachrymans. It is now known that the white eye feathers represent a plumage polymorphism that increases in frequency from south to north (geographic cline). Bridled guillemots occur only in the Atlantic and the proportion of bridled birds increases from zero at the southern limits of the guillemot's range (Portugal - where guillemots are now almost extinct) to about 50% in at the northern limit - near Bear Island, Norway. Interestingly, the very small populations at the very northern limits, in Greenland and Spitzbergen, have relatively low proportions of bridled birds. Whether the bridle has any functional significance is not known.

Photo and text contributed by Professor Tim Birkhead, Department of Zoology, Sheffield University, England. Professor Birkhead has authored numerous publications on the Auks, including books such as 'The Atlantic Alcidae' and 'The Great Auk Islands'.