Effects of backpack and implanted radiotransmitters on captive blue-wingedteal

Radiotelemetry is frequently used for research on waterfowl, but some trans mitter designs alter reproductive effort, behavior, and mass of birds. Quan titative comparisons of transmitter effects are needed so researchers can u se instruments least likely to generate biased results. We compared body ma ss and behavior of captive blue-winged teal (Anas discors) females fitted w ith 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 gain ed mass (P = 0.02). Mass of implanted birds recovered by the second week af ter surgery, and never differed among treatment groups over the subsequent 11 weeks (P greater than or equal to 0.51). Females with backpack transmitt ers 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 differe nce among the treatments in time spent resting (P greater than or equal to 0.18), feeding (P greater than or equal to 0.10), or on locomotion (P great er than or equal to 0.18), except that backpack-marked females spent less t ime engaged in locomotion than did implanted females (P = 0.03). Our result s corroborate previous studies showing effects of back-pack-harness transmi tters on behavior. We demonstrated that implants do not affect behavior. bu t are associated with a temporary; post-surgical loss of mass. The alterati on of behavior caused by backpack transmitters did not diminish with time. so researchers should not assume that all adjustment period is sufficient t o eliminate transmitter effects.