A captive study was conducted to determine the most appropriate method for attaching radio transmitters to a medium-sized (20–100 g) passerine, the European Starling (Sturnus vulgaris). Using mock transmitters, three methods of attachment were tried: a body harness, a glued backpack, and a tail-mount. The harness was the most reliable in terms of duration of attachment, with six of eight attachments (75%) retained by the birds at the completion of the 24-d trial. In contrast, just two of eight (25%) glued backpack attachments remained in place at the conclusion of the study. Tail-mounts performed only slightly better than glued backpacks, with only three of eight tail-mounts remaining in place at the conclusion of the study. Flight, feeding, and perching activities were not affected by the attachments; however, some birds showed initial annoyance toward the mock radio transmitters, inferred by pecking directed at the attachment site. Each attachment method was found to slightly alter the activity (pecking) of the starlings compared to the control group, but this persisted only for the first day following attachment. On the basis of the pecking response, tail-mount attachments were the least aggravating to the birds followed by the harness method. Once adjusted to the attachment, we observed no difference in starling activity, and the body condition of control and treated birds remained similar for the duration of the trials. We recommend the use of the harness for attaching radio transmitters to European Starlings and other similar sized passerines, particularly if birds are expected to molt during the experimental period.
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