Negative effects of inbreeding are ubiquitous in both wild and domesticated species, yet the severity of such inbreeding depression may vary depending on the genetic architecture of traits, which in turn may change with age. Yet, exact quantification of inbreeding effects per se is hampered by the difficulty in detecting variation in the natural occurrence of inbreeding among enough individuals across age classes, and the potential for natural inbreeding to be confounded with parental or environmental quality. Experimental studies in captivity can avoid these problems, with mating combinations that produce both inbred and outbred offspring from the same set of parents in a standardized environment. Since Japanese quail (Coturnix japonica) mate indiscriminately and offspring can be raised independent of the parents, they are an ideal bird species for such an experimental approach. In this project we test for effects of inbreeding over a range of traits (e.g., behaviour, fertility, age-specific survival) and monitor performance over the complete lifespan. This allows us to get a better understanding of for which traits, and at what age, inbreeding depression is most severe.