Evaluation of tag attachment techniques for plunge‐diving terns

Ruben C. Fijn*, Rob S.A. van Bemmelen, Mark P. Collier, Wouter Courtens, E.E. van Loon, Martin J.M. Poot, Judy Shamoun‐Baranes

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


A wide variety of attachment techniques have been used to track birds with electronic tags,with glue, tape, leg rings, neck collars and harnesses being the most common methods. Ingeneral, the choice of attachment method should strive to minimize tagging effects, butensure that sufficient data are collected to address the research question at hand. The aim ofour study was to develop and evaluate tag attachment methods to track Sandwich TernsThalasseus sandvicensisduring the last part of the incubation and the chick-rearing period ofone breeding season. Tag attachments had to stay on for the duration of the chick-rearingperiod (5–6 weeks) and be non-restraining andflexible, but strong enough to withstand theforces and submersion associated with their plunge-diving foraging technique. Wefirstexperimentally tested the durability offlexible material under various environmental condi-tions with the aim of developing a self-releasing harness. Then, infield studies, we comparedthree different attachment methods on terns during the breeding seasons, attaching tags todorsal feathers using (1) tape, (2) glue or (3) a newly developed harness made specificallyfor short-term deployments of one chick-rearing period and constructed from degradablematerial. Assessment of the performance of attachment methods was based on retentiontime of the loggers and on annual survival rates of tagged individuals in comparison withnon-tagged individuals. The use of tape and glue led to premature loss of tags (median mini-mum retention time (range) of 3 (1–4) days and 15 (5–26) days, respectively), whereas theself-releasing harness had a median minimum retention time of 42 (18–91) days, which issufficient to track Sandwich Terns during the entire chick-rearing period. The apparentannual survival of birds tagged using glue or tape did not differ from that observed in non-tagged control birds. In contrast, birdsfitted with the self-releasing harnesses might haveexperienced a lower survival rate than control birds. Entanglement of birds in the harnessmaterial was incidentally observed in three cases, which may have contributed to the lowersurvival rates observed in this group. The risk of entanglement can potentially be mitigatedwith a leg-loop harness instead of a full-body harness. Our results highlight the necessity ofcareful consideration when selecting appropriate attachment methods. Specifically, there isa need to address whether the research questions and desired tracking duration justify theuse of a harness and the higher impact that it entails, or whether a tape or glue-mount is suf-ficient. More broadly, sharingfield expertise in tag attachments across studies is essential tosuccessful deployments while minimizing the impact on animals
Original languageEnglish
Publication statusE-pub ahead of print - 4 Feb 2024


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