Cygnus columbianus By Matt Young March 17, 2014 12:00 MST Cygnus columbianus – tundra swan, Walden Ponds, Boulder, Colorado, March, 2014. A single swan, presumably the same one, has been showing up here for the last few years. I looked for the people with the biggest binoculars and the longest focal-length camera lenses and asked how come there was only one? I got several answers, all of which begged the question why the bird is not in a flock: (1) They mate for life, and maybe this one lost its mate. (2) They mate for life, but maybe they don’t always hang around together. (3) Maybe this one is a juvenile, not old enough to have a mate.