Subcutaneous anchor attachment increases retention of radio transmitters on Xantus' and Marbled Murrelets

We modified a subcutaneous anchor attachment and achieved transmitter reten tion times that exceeded those reported previously for other attachments us ed on alcids. Traditional suture and epoxy attachment methods were used on Xantus' Murrelets in 1995 and 1996, while the modified attachment was used for Xantus' Murrelets in 1996 and 1997 and Marbled Murrelets in 1997. Modif ications included use of an inhalant anesthetic, placing the anchor in a mo re cranial position on the back, application of marine epoxy, and place men t of a single subcutaneous non-absorbable suture at the caudal end of the r adio to hold the radio in place initially. We located 22 of 56 (39%) Xantus ' Murrelets radio-marked using suture and epoxy during aerial surveys in 19 95 and 1996. Of birds radio-marked using the subcutaneous anchor attachment , we located 92 of 113 (81%) Xantus' Murrelets marked in 1996 and 1997 and all 28 (100%) Marbled Murrelets marked in 1997 during aerial surveys. The m aximum confirmed duration for the subcutaneous anchor transmitter attachmen t was 51 d for Xantus' Murrelets and 78 d for Marbled Murrelets versus 41 d for the suture and epoxy attachment wed on Xantus' Murrelets. Recapture ra tes of radio-marked Xantus' Murrelets were similar to recapture rates of un marked Xantus' Murrelets. Our post-release observations indicated negligibl e short-term physical effects from the attachment procedure, while telemetr y data and examination of recaptured murrelets indicated no evidence of inf ection or other long-term physical effects. Breeding behavior of some murre lets was not disrupted; however, further evaluation of potential effects of this attachment technique on breeding and behavior is needed.