Thankyou to Lisa, Stuart, and Serge for raising questions (and supplying some
answers) about the nasal disks being used for Goldeneye...I should have included
more information on this. The disks were one-half inch diameter or one-half by
one-half inch (ca. 1.2 x 1.2 cm) and in the following shapes: circle, square,
triangle, cross, and Y. We used the following colors: white, yellow, orange, and
blue. The disks were attached to the bill, one on each side, using monofilament
(fishing) line fitted through the neres (nasal cavity) and melted into a ball at
the ends. A similar technique was used by JP Savard in the mid-1980s in his
research on Goldeneye. Savard did not observe any problems with the disks; some
of his marked birds returned to nest on their original ponds up to 10 years
later, still retaining their disks. We observed marked birds, including young of
the year, and did not notice any difference in behavior compared to unmarked
birds. This technique appears to be the only good one to mark Goldeneye so that
individuals are recognizable. They rarely, if ever, haul out of water (like
Harlequin Ducks... hence, tarsal bands) and fitting them with neck bands (eg.
Snow Geese) is not a good idea because it probably would interfere with feeding.

I hope this helps. Thanks for the interest.
Sean Boyd