Poor early-life conditions are often associated with increased rates of individual ageing and a reduced lifetime performance. However, the causal pathways behind such effects are poorly known. Experimental manipulations of early-life environmental variables and specific breeding designs, combined with lifelong monitoring of individual performance, are needed to determine the importance of specific variables, and establish whether effects at later age are irreversible. The precociality and relatively short lifespan of Japanese quail (Coturnix japonica) makes them an ideal bird species for such experiments. By experimentally manipulating incubation and chick rearing conditions, and by crossing selection lines with high and low investment in eggs, we are able to exactly quantify how the quality of an individual’s early-life environment translates to lifetime performance as an adult.