Retention and effects of nasal markers and subcutaneously implanted radio transmitters on breeding female Lesser Scaup

Abstract

Forty-seven wild female Lesser Scaup (Aythya affinis) were marked with nasal markers and radio transmitters (implanted subcutaneously on the back) just prior to breeding near Yellowknife, Northwest Territories, in 1999 and 2000. Retention rates of both marker types were evaluated, and their effects on specific behavior categories were assessed by comparison of marked birds with unmarked control birds. Significant effects of nasal markers on behavior were detected; females often removed vegetation from nasal markers after diving, and consequently marked females tended to shake their head more frequently than unmarked birds. No nasal markers were lost during the study. Five females lost radios, producing an average retention time of 39 d. Daily retention rate was 0.997, being 0.85 when extrapolated to 60 d. The survival rate of 42 females radio-tracked consistently was constant for six 7-d intervals, suggesting no immediate adverse effect on survival. Because the technique is invasive, use of subcutaneous transmitters may not be appropriate for all applications, but it could be a preferred alternative to other transmitter-attachment methods for short-term tracking of waterfowl.