Newsom S.E., Hughes B., Russell I.C., Ekins G.R. & Sellers R.M. (2004) Sub-specific differentiation and distribution of Great Cormorants Phalacrocorax carbo in Europe. ARDEA 92 (1): 3-9

The use of biometrics for sub-specific differentiation of Great Cormorants Phalacrocorax carbo in Europe was investigated using skins of known subspecies and showed that gular pouch angle is a useful character for assigning individuals to sub-species. Where further measurements of bill depth and bill length can be taken, sex-specific discriminant functions allow the majority of individuals to be correctly identified to sub-species. The identity of 261 Great Cormorants of unknown sub-species shot (under MAFF licence) on inland water bodies in England during the winters of 1997-98 and 1998-99 were investigated; 66% were P.c. carbo and 34% P.c. sinensis. This suggests that P.c. carbo is currently the predominant sub-species inland in England during the winter. The findings of this paper now allow for long-term and cost-effective monitoring of sub-species occurrence and population development in the UK, as well as in other European countries where the two subspecies may occur