The aim of the study presented in this paper is to disentangle the roles of three mechanisms -- selection, adaptation, and disruption -- in influencing migrant fertility in Ghana. Using data from the 1998 Ghana Demographic and Health Survey, we fit Poisson and sequential logit regression models to discern the effects of the above mechanisms on cumulative fertility and annual probabilities of birth. Characteristics of migrants from four types of migration stream are examined and compared with those of non-migrants at origin and destination. We find substantial support for the selection hypothesis among both rural-urban and urban-rural migrants. Disruption is evident only in the fertility timing of second and higher-order births in Ghana. Our finding that migrants bear children at about the same rates as the natives at destination implies that the growth rate of cities will slow down quickly and that the rural population will continue to have high fertility. Thus to achieve a reduction in the national fertility level, family planning activities need to be directed towards rural areas.