Weak effects of geolocators on small birds: A meta‐analysis controlled for phylogeny and publication bias

Vojtech Brlík*, Jaroslav Koleček, Malcolm Burgess, Steffen Hahn, Diana Humple, Miloš Krist , Janne Ouwehand, Emily L Weiser, Peter Adamik, Jose A. Alves, Debora Arlt, Sanja Barišić, Detlef Becker , Eduardo J. Belda, Václav Beran, C Both, Susana P. Bravo, Martins Briedis, Bohumír Chutný , Davor ĆikovićNathan W Cooper, Joana S Costa, Víctor R. Cueto, Tamara Emmenegger, Kevin Fraser, Olivier Gilg, Marina Guerrero, Michael T. Hallworth , Chris M. Hewson, Frederic Jiguet, James A Johnson, Tosha Kelly, Dmitry Kishkinev, Michel Leconte, Terje Lislevand, Simeon Lisovski, Cosme López, Kent P. McFarland, Peter P. Marra, Steven M. Matsuoka, Piotr Matyjasiak, Christoph M. Meier, Benjamin Metzger, Juan S. Monrós, Roland Neumann, Amy Newman, Ryan Norris, Tomas Pärt, Václav Pavel, Noah G. Perlut, Markus Piha, Jeroen Reneerkens, Christopher C. Rimmer, Amélie Roberto‐Charron, Chiara Scandolara, Natalia Sokolova, Makiko Takenaka, Dirk Tolkmitt, Herman van Oosten, Arndt H. J. Wellbrock, Hazel Wheeler, Johannes van der Winden, Klaudia Witte, Brad Woodworth, Petr Procházka

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Currently, the deployment of tracking devices is one of the most frequently used approaches to study movement ecology of birds. Recent miniaturization of light-level geolocators enabled studying small bird species whose migratory patterns were widely unknown. However, geolocators may reduce vital rates in tagged birds and may bias obtained movement data. There is a need for a thorough assessment of the potential tag effects on small birds, as previous meta-analyses did not evaluate unpublished data and impact of multiple life-history traits, focused mainly on large species and the number of published studies tagging small birds has increased substantially. We quantitatively reviewed 549 records extracted from 74 published and 48 unpublished studies on over 7,800 tagged and 17,800 control individuals to examine the effects of geolocator tagging on small bird species (body mass <100 g). We calculated the effect of tagging on apparent survival, condition, phenology and breeding performance and identified the most important predictors of the magnitude of effect sizes. Even though the effects were not statistically significant in phylogenetically controlled models, we found a weak negative impact of geolocators on apparent survival. The negative effect on apparent survival was stronger with increasing relative load of the device and with geolocators attached using elastic harnesses. Moreover, tagging effects were stronger in smaller species. In conclusion, we found a weak effect on apparent survival of tagged birds and managed to pinpoint key aspects and drivers of tagging effects. We provide recommendations for establishing matched control group for proper effect size assessment in future studies and outline various aspects of tagging that need further investigation. Finally, our results encourage further use of geolocators on small bird species but the ethical aspects and scientific benefits should always be considered.

Original languageEnglish
Pages (from-to) 207-220
Number of pages14
JournalJournal of Animal Ecology
Issue number1
Early online date16-Feb-2019
Publication statusPublished - Jan-2020


  • geolocation
  • tracking methods
  • migration
  • geolocator
  • geolocator, GeoLight, FLightR, migration, annual schedules, precision

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