Recognizing individual Bewick's Swans by bill pattern

Abstract

The background to the identification by bill pattern of Bewick's Swans Cygnus columbianus bewickii is given, followed by description of bill pattern development up to and following the third winter. A recognition test demonstrated the reliability of identification by bill pattern, even over a period of years, and that experience of the observer increases proficiency. The problem of storing large numbers of bill patterns are discussed, other clues to identification mentioned, and a recommendation is made that at present identification by bill patterns is better for short rather than long-term studies.