EFFECTS OF RADIO TRANSMITTERS ON NESTING CAPTIVE MALLARDS

Radio packages may subtly affect bird behavior and condition, and thus could bias results from studies using this technique. To assess effec ts on reproduction of mallards (Anas platyrhynchos), we tested 3 types of back-mounted radio packages on captive females. Eight paired femal es were randomly assigned to each of 4 treatments: 4-g transmitter att ached with sutures and glue, 10-g or 18-g transmitter attached with a harness, and no transmitter (control). All mallards were fed ad libitu m. No differences were detected among treatments in number of clutches , clutch size, nesting interval, egg mass, or body mass; powers (range = 0.15-0.48) of tests were low. Feather wear and skin irritation arou nd radio packages were minimal. Birds retained sutured transmitters fo r an average of 43.5 days (range = 3-106 days) and harness transmitter s for the duration of the study (106 days). Sutures were not reliable and presently are not recommended as an attachment method. caution is advised in applying these results to radio-equipped mallards in the wi ld.