In 2000 and 2001, we determined the sex of 80 adult Razorbills Alca torda caught on Machias Seal Island, New Brunswick, Canada, 71 birds in 2000 and 9 in 2001. Sex was determinedfor the 2000 birds using DNA from feathers, and for the 2001 captures using behavioural observations. Males averaged significantly larger than females in head+bill (3% larger), culmen (3%) and bill depth (4%). Discriminant Function Analysis (DFA) was used to classify birds that were not sexed. The function correctly classified 78% of birds using the linear measurements (head+bill, bill depth, wing chord, and tarsus) and 79% when a stepwise procedure was used. The highest classification success rate (80%) resulted from using only head+bill and bill depth. Bill size of Razorbills from Quebec and Labrador is very similar to those from Machias Seal Island, suggesting that the functions reported here may apply throughout the North American breeding population.

Atlantic seabirds

CC BY 3.0 NL ("Naamsvermelding")

Nederlandse Zeevogelgroep

V.D. Grecian, A.W. Diamond, & J.W. Chardine. (2003). Sexing Razorbills Alca torda breeding at Machias Seal Island, New Brunswick, Canada, using discriminant function analysis. Atlantic seabirds, 5(2), 73–80.