Weak Effects of Geolocators on Small Birds: A Meta-analysis Controlled for Phylogeny and Publication Bias

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need for a thorough assessment of the potential tag effects on small birds, as previous meta-analyses did not evaluate unpublished data and impact of multiple life-history traits, focused mainly on large species and the number of published studies tagging small birds has increased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 We quantitatively reviewed 549 records extracted from 74 published and 48 unpublished studies on over 7,800 tagged and 17,800 control individuals to examine the effects of geolocator tagging on small bird species (body mass 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.Grantova Agentura Ceske Republiky 13-06451SInstitut Polaire Francais Paul Emile Victor IPEV-1036Institutional Research Plan RVO: 68081766Leverhulme Trust RPG-2013288Russian Foundation for Basic Research Arctic-18-05-60261Russian Science Foundation 17-14-0114

The effect of climate change on avian offspring production: A global meta-analysis

Climate change affects timing of reproduction in many bird species, but few studies have investigated its influence on annual reproductive output. Here, we assess changes in the annual production of young by female breeders in 201 populations of 104 bird species (N = 745,962 clutches) covering all continents between 1970 and 2019. Overall, average offspring production has declined in recent decades, but considerable differences were found among species and populations. A total of 56.7% of populations showed a declining trend in offspring production (significant in 17.4%), whereas 43.3% exhibited an increase (significant in 10.4%). The results show that climatic changes affect offspring production through compounded effects on ecological and life history traits of species. Migratory and larger-bodied species experienced reduced offspring production with increasing temperatures during the chick-rearing period, whereas smaller-bodied, sedentary species tended to produce more offspring. Likewise, multi-brooded species showed increased breeding success with increasing temperatures, whereas rising temperatures were unrelated to repro- ductive success in single-brooded species. Our study suggests that rapid declines in size of bird populations reported by many studies from different parts of the world are driven only to a small degree by changes in the production of young

Data from: The importance of competition for food and nest-sites in aggressive behaviour of Collared Flycatcher Ficedula albicollis

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Data from: The importance of competition for food and nest-sites in aggressive behaviour of Collared Flycatcher Ficedula albicollis

Capsule: Using an experimental approach, this study disentangles effects of two important sources on the elicitation of aggressive interspecific behaviour. Aims: Although interspecific competition for nest sites is broadly assumed to be an example of interference, there are no experimental studies supporting this idea. Here the importance of competition for nest sites and food for the elicitation of aggressive behaviour of a secondary cavity-nesting bird are investigated. Methods: The Collared Flycatcher’s Ficedula albicollis responses to mounts of the Great Tit Parus major (nest site and food competitor), Chaffinch Fringilla coelebs (food competitor) and Dunnock Prunella modularis (control species) were tested. Trials were performed near flycatchers’ nests during nest building, incubation and care of nestlings. Results: The intensity of dive attacks and frequency of contact attacks showed that the aggression of Collared Flycatchers decreased in the direction: Great Tit > Chaffinch > Dunnock. The difference in aggressiveness was greater between Great Tit and Chaffinch than between Chaffinch and Dunnock. Aggression directed toward Great Tits increased from the nest building to the incubation stage and then decreased markedly in the nestling stage. Males were more aggressive than females. Conclusion: These results suggest that competition for nest sites, and to a lesser extent for food, may be of an interference nature and that the reproductive value hypothesis can only partly explain differences in the Collared Flycatcher’s defensive behaviour found between sexes and stages of the breeding cycle

Data from: Short- and long-term effects of egg size and feeding frequency on offspring quality in the collared flycatcher (Ficedula albicollis)

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