Early examples of capture-recapture data typically only presented information on the life-histories of animals. More recently such data are accompanied by additional, covariate information. If this can be successfully incorporated into models then understanding of underlying mechanisms can be enhanced, and models are also validated; so incorporating covariates is clearly very important. For example, it is known that sea-bird populations in the North Sea have experienced periods of substantial decline in recent years. However, in that case there appears to be no relationship with obvious covariates, such as the temperature of the sea and the availability of food, or lagged versions of these. Covariates may be used in models for closed populations, to account for heterogeneity in capture probabilities, in open models where the focus is the estimation of survival, in stopover models, in occupancy models, etc. In this chapter we consider a wide range of applications, for several different species.