Data and code for: Optimal clutch size revisited: separating individual quality from the costs of reproduction

Life-history theory, central to our understanding of diversity in morphology, behaviour and senescence, describes how traits evolve through the optimisation of trade-offs in investment. Despite considerable study, there is only minimal support for trade-offs within species between the two traits most closely linked to fitness – reproduction and survival – questioning the theory’s general validity. We used a meta-analysis to separate quality effects from the costs of reproduction using studies of parental investment and survival in birds. Experimental enlargement of broods caused reduced parental survival. However, the effect of experimental enlargements was small and opposite to the effect of phenotypic quality, where individuals that naturally produced larger clutches also survived better. The opposite effects on survival in experimental and observational studies of parental care provide the first meta-analytic evidence for theory suggesting that quality differences mask trade-offs. Fi..., ,