Egg components vary independently of each other in the facultative siblicidal Black-legged Kittiwake Rissa tridactyla

Vallarino, Adriana; Evans, Neil; Daunt, Francis; Wanless, Sarah; Nager, Ruedi. 2012 Egg components vary independently of each other in the facultative siblicidal Black-legged Kittiwake Rissa tridactyla. Journal of Ornithology, 153 (2). 513-523.

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Egg composition varies both within and between clutches, and mothers are expected to alter their deposition of resources to the egg depending on environmental conditions and breeding strategies. Within-clutch variation in egg composition has been proposed to reflect an adaptive maternal strategy influencing sibling competition. In species with brood reduction, mothers should reinforce brood hierarchies due to hatching asynchrony and favour senior chicks by making first-laid eggs larger, richer in nutrients, with higher testosterone and carotenoid levels and lower corticosterone concentrations than last-laid eggs [parental favouritism hypothesis (PFH)]. Moreover, mothers that are of better quality and/or experience better feeding conditions during laying are expected to increase their deposition of resources to the egg, resulting in differences between clutches [investment hypothesis (IH)]. Several components may act together to provide an optimal reproductive strategy, but studies of variation in different egg components in the same egg are relatively rare. We analysed egg size, testosterone and corticosterone concentrations and carotenoids measured as yolk colour between and within clutches for the facultative siblicidal Black-legged Kittiwake Rissa tridactyla. First-laid eggs were larger, contained lower testosterone, higher yolk colour score, and similar corticosterone levels than last-laid eggs. Thus, only differences in egg size and yolk colour supported the PFH. We used within-clutch egg size dimorphism as an indicator of the quality of the mother or the feeding conditions during laying. In support of the IH, we found that mothers of better quality or that experienced better feeding conditions deposited more corticosterone into their eggs. High corticosterone levels may benefit nestlings when there is no brood reduction but high sibling competition is present. We found no support for the hypothesis that egg components are mutually adjusted to each other and we discuss the possible reasons for this.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Topics & Objectives 2009 - 2012 > Biodiversity
UKCEH and CEH Sections/Science Areas: Watt
ISSN: 0021-8375
Additional Information. Not used in RCUK Gateway to Research.: This document is the author’s final manuscript version of the journal article, incorporating any revisions agreed during the peer review process. Some differences between this and the publisher’s version remain. You are advised to consult the publisher’s version if you wish to cite from this article. The final publication is available at
Additional Keywords: behavioral endocrinology, parental investment theory, ecological/evolutionary physiology, seabirds, maternal effects
NORA Subject Terms: Ecology and Environment
Date made live: 21 Jan 2013 13:54 +0 (UTC)

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