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Brain size mediates the choice of breeding strategy in the red‐backed shrike Lanius collurio
AbstractThe brain size of vertebrates represents a trade‐off between natural selection for enhanced cognitive abilities and the energetic constraints of brain tissue production. Processing information efficiently can confer benefits, but it also entails time costs. Breeding strategies, encompassing timing of breeding onset and nest‐site selection, may be related to brain size. In this study, we aim to elucidate the relationship between brain size, breeding timing, nest‐site choice, and breeding success in the red‐backed shrike Lanius collurio. Our findings revealed that the timing of the first egg‐laying date was associated with female head size, with larger‐headed females tending to lay eggs later in the breeding season. Additionally, we observed that breeding success was positively correlated with increased nest concealment. However, this relationship was stronger in males with smaller heads. In turn, nest concealment was not related to head size but primarily influenced breeding onset. These results suggest that the choice of breeding strategy may be moderated by brain size, with differences between sexes. Larger‐headed females may invest more time in selecting nesting sites, leading to delayed breeding onset, while larger‐headed males may compensate for suboptimal nest concealment. Our study sheds light on the intricate interplay between brain size, breeding timing, nest‐site preferences, and breeding success in passerine birds, underscoring the potential role of cognitive capacity in shaping individual decision‐making processes.
The prevalence of anthropogenic nest materials differs between two distinct populations of migratory birds in Europe
AbstractA major impact of human development is the transformation of natural habitats into farming lands and the expansion of built-up areas. Also, plastic pollution is affecting wildlife on a global scale. Discarded plastic is ubiquitous and accessible for birds, which can incorporate them into the nest structure. Here, we describe the differences in type, prevalence, and the amount of anthropogenic nest materials between two populations of terrestrial, mainly farmland bird, the white storkCiconia ciconia, on a broad geographical scale, from two migratory divides—eastern in Poland and western in Spain (in total 303 nests). In the two populations, we detected significant differences in the incorporation of anthropogenic nest material, as measured by the Human Footprint Index (HFI) and the Impervious Surface Areas (ISA). We found that ISA was positively related to anthropogenic nest material incorporation in the Spanish population, and HFI was positively related to anthropogenic nest material, in contrast to the Polish population, in which the relationships were not significant. Moreover, we showed that the prevalence of nests with anthropogenic nest material was two times higher in Spanish than in the Polish white stork population. This study demonstrates that the behavior of incorporation of the anthropogenic nest material differs between two distinct populations of a single bird species.