This is the second in a series of three interrelated papers which aim to combine evolutionary migration models with stochastic utility theory. The first paper dealt with migratory dynamics. Here the details are given of a choice model, established by McFadden, which can be used in conjunction with migratory dynamics thus providing an explicit link between the macroproperties of the population system and human behaviour. First, the structure of transition probabilities is derived under a two-level decision to migrate. An argument is then given about the empirical form of these probabilities, and the discussion closes with a method which can be used for their maximum likelihood estimation.