Migration is a major household survival option for both the rich and the poor in many developing countries. In rural Kenya, access to land for the poor is fundamental to their survival, with lack of access often resulting in migration. The Chyulu Hills settlements are in a remote region bordering two protected areas, the Tsavo and the Chyulu Hills National Parks. They have a complex history of squatter occupation and secondary migrations, which often end in violent evictions and land expropriation to settle more squatters. We provide an analysis of migration dynamics by identifying patterns, trends, and drivers of population mobility over the past 30 years. We collected data at both household and village level, and used binary logistic models to reveal the proximate and exogenous causes of secondary squatter migration. We used geographical information systems to generate a data set of village access and to map immigrant origins and patterns of village establishment. Migration to the Chyulu Hills is widespread, and secondary migrations are common. Policy factors such as land tenure, issuance of free land, and provision of schools were the strongest factors in changing the odds of migration. Although landlessness in the Chyulu Hills seems widespread, this study revealed that policy was stronger and consistently more influential in determining whether complete households re-migrated or stayed. This may override or emphasise the role of some classic migration drivers. Copyright © 2010 John Wiley & Sons, Ltd.