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MEPS prepress abstract   -  DOI:

Tags below three percent of body mass increase nest abandonment by rhinoceros auklets, but handling impacts decline as breeding progresses

Alice Sun, Shannon Whelan*, Scott A. Hatch, Kyle H. Elliott

*Corresponding author:

ABSTRACT: Biologging has revealed many of the mysteries surrounding seabird behavior far from land. However, tagging seabirds with biologgers may influence the very traits they are designed to observe. Such ‘tag effects’ are often argued to be minimal below a threshold of 3% of body mass. Nonetheless, few studies carefully separate handling from tagging effects, so the effect of tag size is often confounded with the effect of handling. Puffins, including rhinoceros auklets, are notoriously difficult to work with due to high abandonment rates. To examine tagging and handling effects in rhinoceros auklets (Cerorhinca monocerata), we compared abandonment rates of individuals equipped with a GPS weighing ~2.3% of body mass with abandonment rates of birds handled but not equipped, and of birds not handled at all (controls). Handling more than doubled abandonment rates compared to control birds and tagging more than doubled abandonment rates compared to birds that were handled but not tagged. Abandonment rates decreased as incubation progressed and were lowest during chick-rearing; we did not, however, find differences abandonment among tagged birds in late incubation and early chick-rearing, possibly due to small sample sizes or similarity between these two breeding stages. We found the egg flotation technique particularly useful in estimating egg age, which can help reduce disturbance to a nest site. We conclude that both handling and tagging of auklets increase abandonment, and that effects are lowest during chick-rearing.