Conant et al. (1991) describe swan survey methods used by the U.S. Fish and Wildlife Service in Alaska and present the results of surveys using these methods.
Full citation: Conant, B., J.I. Hodges, and J. G. King. 1991. Continuity and advancement of trumpeter swan Cygnus buccinator and tundra swan Cygnus columbianus population monitoring in Alaska. Pages 125-136 in J. Sears and P.J. Bacon (Eds.) 1991. Proc. Third IWRB International Swan Symposium, Oxford 1989. Wildfowl Supplement No. 1.