Razorbill (Alca torda) Science Article 4
Razorbills Alca torda were measured in one Russian and five Norwegian colonies. A comparison with measurements from colonies in Britain, Ireland, Iceland and the Baltic Sea shows a clear correlation with the geographical position of each colony and a clinal increase in size from the south-west to north-east. Wing length and gonys depth were negatively correlated with surrounding summer sea-surface temperatures. Due to considerable overlap in measurements within the range of the cline, caution is advised when identifying geographical origins of Razorbills on the basis of their size alone.
Robert T. Barrett, Tycho Anker-Nilssen & Yuri V. Krasnov 1997, Marine Ornithology 25: 5-8.