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Type: Journal article
Title: First light for avian embryos: eggshell thickness and pigmentation mediate variation in development and UV exposure in wild bird eggs
Author: Maurer, G.
Portugal, S.
Hauber, M.
Mikšík, I.
Russell, D.
Cassey, P.
Citation: Functional Ecology, 2015; 29(2):209-218
Publisher: Wiley
Issue Date: 2015
ISSN: 0269-8463
Statement of
Golo Maurer, Steven J. Portugal, Mark E. Hauber, Ivan Mikšík, Douglas G. D. Russell and Phillip Cassey
Abstract: 1. The avian embryo's development is influenced by both the amount and the wavelength of the light that passes through the eggshell. Commercial poultry breeders use light of specific wavelengths to accelerate embryonic growth, yet the effects of the variably patterned eggshells of wild bird species on light transmission and embryonic development remain largely unexplored. 2. Here, we provide the first comparative phylogenetic analysis of light transmission, through a diverse range of bird eggshells (74 British breeding species), in relation to the eggshell's thickness, permeability, pigment concentration and surface reflectance spectrum (colour). 3. The percentage of light transmitted through the eggshell was measured in the spectral range 250–700 nm. Our quantitative analyses confirm anecdotal reports that eggshells filter the light of the externally coloured shell. Specifically, we detected a positive relationship between surface eggshell reflectance (‘brightness’) and the percentage of light transmitted through the eggshell, and this relationship was strongest at wavelengths in the human-visible blue-green region of the spectra (c. 435 nm). 4. We show that less light passes through thicker eggshells with greater total pigment concentrations. By contrast, permeability (measured as water vapour conductance) did not covary significantly with light transmission. Eggs of closed-nesting species let more light pass through, compared with open nesters. 5. We postulate that greater light transmission is required to assist embryonic development under low light exposure. Importantly, this result provides an ecological explanation for the repeated evolution of immaculate, white- or pale-coloured eggshells in species nesting in enclosed spaces. 6. Finally, we detected correlative support for the solar radiation hypothesis, in that eggshells of bird species with a longer incubation period let significantly less of the potentially harmful, ultraviolet (UV) light pass through the eggshell. In summary, we demonstrate suites of avian eggshell properties, including eggshell structure and pigmentation, which are consistent with an evolutionary pressure to both enhance and protect embryonic development.
Keywords: breeding birds; eggshell colour; light transmission; nesting behaviour; pigments; ultraviolet light
Description: Article first published online: 29 JUL 2014
Rights: © 2014 The Authors. Functional Ecology © 2014 British Ecological Society
RMID: 0030015983
DOI: 10.1111/1365-2435.12314
Grant ID:
Appears in Collections:Ecology, Evolution and Landscape Science publications

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