Blue-green eggshell coloration is not a sexually selected signal of female quality in an open-nesting polygynous passerine |
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Authors: | Marcel Honza Milica Požgayová Petr Procházka Michael I Cherry |
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Institution: | 1.Institute of Vertebrate Biology,Academy of Sciences of the Czech Republic,Brno,Czech Republic;2.Department of Botany and Zoology,University of Stellenbosch,Matieland,South Africa |
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Abstract: | It has been proposed that blue-green egg colours have evolved as a post-mating signal of female quality, selected by males
allocating their parental effort in response to the strength of this signal. We tested two main assumptions of the sexually
selected egg coloration hypothesis: (1) whether the intensity of eggshell blue-green chroma (BGC) reflects female quality;
and (2) whether males make their decisions on the level of parental care that they provide according to the intensity of eggshell
BGC. As a model species, we chose the facultatively polygynous great reed warbler (Acrocephalus arundinaceus). In this species, females simultaneously paired with the same male, compete for his nest attendance and could benefit from
signalling their quality through egg coloration. However, we found no association between the variation in eggshell BGC and
the measures of female quality (physical condition, mean egg volume and age). Moreover, great reed warbler males did not adjust
their investment (as measured in terms of nest defence against a brood parasite) in relation to the eggshell BGC. We conclude
that blue-green egg coloration in this open-nesting passerine is unlikely to have a signalling function. Rather, the large
colour variation among clutches of individual females may depend on yearly fluctuations in environmental conditions. |
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