Maternal investment in eggs is affected by male feet colour and breeding conditions in the blue-footed booby, Sula nebouxii
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Females are expected to vary investment in offspring according to variables that may influence the offspring fitness in a way that optimises her inclusive fitness for a particular context. Thus, when sexual ornaments signal the quality of the male, females might invest in reproduction as a function of the attractiveness of their mate. We tested whether breeding conditions and male feet colour influence reproductive decisions of blue-footed booby females. In the blue-footed booby, male feet colour is a dynamic condition-dependent sexually selected trait that is related to paternal effort. During two consecutive years, an El Niño year (poor breeding conditions) and a year with good breeding conditions, we experimentally reduced male attractiveness by modifying their feet colour after the first egg was laid and recorded female investment in the second egg. We found that, relative to the first egg in the clutch, females laid heavier second eggs during the poor year than during the good year. Females paired with males with duller feet colour reduced second-egg mass and volume and delayed the laying of the second egg, independently of the year. Absolute yolk androstenedione (A4) concentration (but not testosterone, T) in second eggs was higher during a poor year than during a good year. Only during a year with poor breeding conditions, females paired with experimental males decreased the relative A4 concentration (but not T) in the second egg compared to control females. Thus, blue-footed booby females probably favour brood reduction by decreasing egg quality and increasing size asymmetry between chicks when the breeding and the mate conditions are poor.
KeywordsSexual traits Egg quality Laying asynchrony Yolk androgens Sula nebouxii Maternal effects
We are grateful to M. Cerbón, A. Córdoba, H. Drummond, D. Gil, A. Velando, K. Renton, two anonymous Referees and J. Graves for helpful comments and discussion during the study, to E. Villaseñor, D. Gonzalez and A. Nava Sánches for their great help during field work and to the Laboratorio de Hormonas Esteroides del Instituto Nacional de Ciencias de la Salud y de Nutrición for logistic support for the androgen determination. The project was supported by the Universidad Nacional Autónoma de México (UNAM, PAPIIT IN211406) and CONACYT (47599). Logistic support was provided by the Armada de México, the staff from the Parque Nacional Isla Isabel and the fisherman from San Blas, Nayarit. The experiments comply with the current laws of Mexico; permissions were granted by SEMARNAT and the Parque Nacional Isla Isabel. During the study, F. Dentressangle was supported by a scholarship for graduate studies from UNAM.
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