Maternal condition but not corticosterone is linked to offspring sex ratio in a passerine bird

Roulin, A., Henderson, L. J., Evans, N. P. , Heidinger, B. J., Adams, A. and Arnold, K. E. (2014) Maternal condition but not corticosterone is linked to offspring sex ratio in a passerine bird. PLoS ONE, 9(10), e110858. (doi: 10.1371/journal.pone.0110858) (PMID:25347532) (PMCID:PMC4210198)

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There is evidence of offspring sex ratio adjustment in a range of species, but the potential mechanisms remain largely unknown. Elevated maternal corticosterone (CORT) is associated with factors that can favour brood sex ratio adjustment, such as reduced maternal condition, food availability and partner attractiveness. Therefore, the steroid hormone has been suggested to play a key role in sex ratio manipulation. However, despite correlative and causal evidence CORT is linked to sex ratio manipulation in some avian species, the timing of adjustment varies between studies. Consequently, whether CORT is consistently involved in sex-ratio adjustment, and how the hormone acts as a mechanism for this adjustment remains unclear. Here we measured maternal baseline CORT and body condition in free-living blue tits (Cyanistes caeruleus) over three years and related these factors to brood sex ratio and nestling quality. In addition, a non-invasive technique was employed to experimentally elevate maternal CORT during egg laying, and its effects upon sex ratio and nestling quality were measured. We found that maternal CORT was not correlated with brood sex ratio, but mothers with elevated CORT fledged lighter offspring. Also, experimental elevation of maternal CORT did not influence brood sex ratio or nestling quality. In one year, mothers in superior body condition produced male biased broods, and maternal condition was positively correlated with both nestling mass and growth rate in all years. Unlike previous studies maternal condition was not correlated with maternal CORT. This study provides evidence that maternal condition is linked to brood sex ratio manipulation in blue tits. However, maternal baseline CORT may not be the mechanistic link between the maternal condition and sex ratio adjustment. Overall, this study serves to highlight the complexity of sex ratio adjustment in birds and the difficulties associated with identifying sex biasing mechanisms.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Heidinger, Dr Britt and Evans, Professor Neil and Henderson, Ms Lindsay and Arnold, Dr Kathryn
Authors: Roulin, A., Henderson, L. J., Evans, N. P., Heidinger, B. J., Adams, A., and Arnold, K. E.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:PLoS ONE
Publisher:Public Library of Science
Copyright Holders:Copyright © 2014 The Authors
First Published:First published in PLoS ONE 9(10):e110858
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
527591Responsive PhD - NERC DTG (N. Metcalfe)Neil MetcalfeNatural Environment Research Council (NERC)NE/H526886/1RI BIODIVERSITY ANIMAL HEALTH & COMPMED