Based on existing bibliographic information, unpublished data, and field work. the evolution of the distribution of the European Starling (Sturnus vulgaris L.) and the Spotless Starling (Sturnus unicolor Temm.) in the Iberian Peninsular during the last 30 years is reconstructed. The European Starling colonized the Peninsula in 1960, with a general rate of expansion (1974-87) of 3.6 km yr-1. The Spotless Starling started its expansion in the 1950s, colonizing the east and the north of the Peninsula at a rate of 4.7 km yr-1 (1960-87), with partials of 5.4 km yr-1 (1960-79), 4.6 km yr-1 (1979-84) and 4 km yr-1 (1984-87). These rates of expansion are equally low for both species, and can be explained by the mountainous configuration and the great areas of forest and shrubs of the Peninsula, which make it difficult for the starlings to move forward, since they are birds primarily adapted to crops and pastures. Where the species have come into contact, sympatric areas have appeared, which have slowed down the process of expansion of both starlings. This is a good example of competition acting as a limiting factor in the dispersal of species.
