Showing papers by "Ruedi G. Nager published in 2004"
TL;DR: A protein–rich diet prior to laying improved maternal body weight prior to breeding compared with birds on a protein–poor diet and gave rise to offspring with lower fecundity than offspring from birds in a better nutritional state.
Abstract: Maternal effects, in which differences in parental state cause differences in offspring fitness, are important in trade-offs influencing an individual's optimal reproductive strategy. In zebra finches (Taeniopygia guttata) we manipulated the nutritional state for four weeks before the start of breeding through protein supplementation. Zebra finches were kept on identical diets during the rest of the experiment. We then tested the effects of maternal state on offspring size, survival and fecundity. In order to separate the effects of maternal state occurring through egg production, incubation and chick-rearing, we used a cross-fostering experiment. We show that a protein-rich diet prior to laying improved maternal body weight prior to breeding compared with birds on a protein-poor diet. Poorer maternal state prior to breeding gave rise to offspring with lower fecundity than offspring from birds in a better nutritional state. Maternal state is thought to affect the conditions developing offspring experience through the bird's ability to produce and incubate eggs. Male and female embryos differed in their responses to conditions at different developmental stages. This shows that embryonic developmental conditions and sex differences in vulnerability to these conditions need to be incorporated into future models of selection, life-history evolution and sex-ratio theory.
106 citations
Journal Article•
TL;DR: It is concluded that delaying the hatching of the brood when caterpillars are late yields a net gain in fitness and thus is a strategy rather than the consequence of energy constraints during the laying and incubation period.
Abstract: We analysed egg-hatching rates, the resulting clutch size and fledging weights in relation to prey abundance in Great Tits Parus major in a mixed deciduous forest in Switzerland We show that the number of oaks within 20 m from the nest affected both clutch size and fledging weight positively During a cold spell females delaying the hatching of their clutch incurred a cost in terms of reduced hatching success On the other hand they readjusted the nestling period of their brood to the delayed caterpillar peak Thus, fledging weights were higher compared to non-delayed broods Since fledging mass is a decisive determinant of post-fledging survival and recruitment, we conclude that delaying the hatching of the brood when caterpillars are late yields a net gain in fitness and thus is a strategy rather than the consequence of energy constraints during the laying and incubation period
21 citations