Editor´s Choice - Negative Impact of geolocators

Submitted by avianbiology on 4 September 2014.

Tiny light-level geolocators with a mass of less than 1 gram give great hopes that it will be possible to reveal the annual migratory journeys of many small songbirds on an individual level, but evidence are also accumulating that equipping a small bird with a geolocator may have a clearly negative impact depending on species, sex and geolocator design. In this extensive and well-controlled study it is demonstrated that adding a 0.7 gram geolocator to a barn swallow with a body mass of about 18 g causes significantly reduced annual survival, delayed onset of breeding the next year and reduced clutch size (among females). However, geolocator deployment on swallow parents did not negatively affect their nesting success in the short term, and there were also indications that improvements in mass, design and attachment of geolocators could alleviate some of the most negative fitness consequences. These results stress the importance of taking great care to test and avoid harmful effects of the geolocators before embarking on large-scale studies, not least of small and aerial species.

Thomas Alerstam, Editor in Chief

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Editor´s Choice