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Avian plumage and eggshell colouration covary with sex-specific contributions to nest building

Citation

Nagy, Jenő; Hauber, Mark E.; Mainwaring, Mark C. (2021), Avian plumage and eggshell colouration covary with sex-specific contributions to nest building, Dryad, Dataset, https://doi.org/10.5061/dryad.8kprr4xmq

Abstract

Interspecific variation in sex-specific contributions to nest building remain poorly understood. We examine whether the colouration of parents and of eggs influences sex-specific nest building contributions in 521 species of Western Palearctic birds. Having colourful plumage and laying colourful eggs are costly because of the deposition of pigments (in feathers and eggs) and/or forming costly nanostructural substrates (of feathers). We tested the hypotheses that species in which females alone build nests (i) exhibit sexual plumage dichromatism and (ii) lay less colourful eggs because they trade-off investment in nest building and egg laying with investment in costly colouration. Using a phylogenetically-informed comparative approach, we found support for the former and for the opposite of the latter prediction. More broadly, the results suggest that sex differences in plumage and egg coloration can influence female pre-copulatory investment in reproduction and, thus, increases our understanding of the linkage and dynamics of animal colouration and parental investment patterns.

Methods

We quantified nest building contributions, and the colouration of parent birds and their eggs of 521 bird species, included in the Birds of the Western Palearctic book series. Nest building contributions were classified as being ‘male’ if males build nests alone, ‘female’ if females build nests alone, ‘both’ if both parents contribute to nest building and ‘neither’ if none of the parents contribute to nest building (e.g. seabirds). Sexual plumage dimorphism was classified as being either present or absent. Data on clutch sizes and body mass of males and females were extracted from the same source and were averaged per species. Eggshell colour was determined by reading species descriptions and by inspecting colour plates and were defined as being blue, brown or white. We deemed blue or brown but not white (unpigmented) as pigmented by predominantly biliverdin or protoporphyrin IX, respectively.

Usage Notes

Variable names and descriptions

Species - scientific name of bird species
Nest_builder - nest builder sex (both, male, female, neither)
Colour_dichromatism - sexual plumage dichromatism (yes/no)
Egg_colur - egg colouration (blue, brown, white)
Mean_BM - average adult body mass in gram
Clutch_size_mean - average clutch size