Effects of Backpack and Implanted Radiotransmitters on Captive Blue-Winged Teal

Radiotelemetry is frequently used for research on waterfowl, but some transmitter designs alter reproductive effort, behavior, and mass of birds. Quantitative comparisons of transmitter effects are needed so researchers can use instruments least likely to generate biased results. We compared body mass and behavior of captive blue-winged teal (Anas discors) females fitted with either a backpack-harness transmitter, abdominally implanted device, or no radio over a 12-week period. Females with implants lost mass during the first week following surgery, while backpack-marked and control birds gained mass (P = 0.02). Mass of implanted birds recovered by the second week after surgery, and never differed among treatment groups over the subsequent 11 weeks (P ≥ 0.51). Females with backpack transmitters spent more time on comfort movements (P < 0.001) and less time in water (P < 0.001) than did birds with implants or no radios. We found no difference among the treatments in time spent resting (P ≥ 0.18), feeding (P ≥ 0.10), or on locomotion (P ≥ 0.18), except that backpack-marked females spent less time engaged in locomotion than did implanted females (P = 0.03). Our results corroborate previous studies showing effects of backpack-harness transmitters on behavior. We demonstrated that implants do not affect behavior, but are associated with a temporary post-surgical loss of mass. The alteration of behavior caused by backpack transmitters did not diminish with time, so researchers should not assume that an adjustment period is sufficient to eliminate transmitter effects.