Razorbill (Alca torda) Science Article 2
Observations of banded birds on Skokholm were made during daily visits to the cliffs between mid-March and mid-August (1971-73), and the work was continued by the staff of the Bird Observatory in 1974. In one study colony, The Bluffs, visited daily throughout the season, the birds became tame, and there was a high probability of identifying all color-banded birds present. Only two records (out of a possible 86) relate to birds that were missed in one year but seen in the next (2%), compared with 19 out of 226 (8%) for the other colonies on Skokholm and 31 out of 118 (26%) for the study colony on Skomer.
C. S. Lloyd and C. M. Perrins, Bird-banding Summer, 1977