The paper is based on field surveys of two locations of rural West Bengal during the1990s. It presents contrasting scenarios of fertility behaviour and its transition for a tribe, namely Santals, between two locations as well as between Santals and lower caste people in the same village. The Santals of Chitrihutu, who migrate seasonally, evince not only low fertility, but they indeed appear far ahead of non-migrating Santals of Thupsara in terms of contraceptive practices and fertility control. The positive role of seasonal migration in hastening fertility transition has been the central message of the present study.