We studied the movements of little egrets Egretta garzetta from breeding colonies in northern Spanish Atlantic estuaries using sighting data of colour-ringed birds. Data on 304 resightings of 95 out of 457 little egrets ringed as chicks in two colonies on the southern Bay of Biscay were analysed. Most egrets (68.9%) were observed less than 50 km from their natal colonies and thus exhibited low dispersal, supporting the view that these birds belong to a resident population breeding along the coasts of the Bay of Biscay. Nearly all resightings (95.5%) occurred in estuaries across an east-west axis corresponding to the Atlantic coast of northern Spain and had a west-biased dispersal direction. We suggest that the recently formed northern Atlantic Spanish population is a consequence of a westward colonisation pattern originating in the French Atlantic colonies.