Combining different sources of data in a single model has been done frequently in fishery sciences for years. Combining different types of data can lead to higher precision in parameter estimates, and even allow the estimation of parameters that can not be estimated using any single data set (e.g. immigration). In terrestrial ecology, it is referred to as “integrated population modelling”, and there has been a considerable increase in its use. Integrated population models owe this new popularity and recent success not only to their technical advantages, but also to the BUGS language which makes flexible bayesian modelling easily accessible to biologists.