SummarySummer bird populations were studied in ten sites: two heathlands, two maritime pinePinus pinasterplantations, one, four, seven and 13‐year‐old eucalyptEucalyptus globulusplantations, one climax oakQuercus roburwoodland, and a farmland area in northwestern Galicia, Spain. The farmland and oak wood contained the greatest number of species (24 and 17 respectively) while the one and four‐year‐old eucalypt stands contained the fewest species (four and six respectively). Avian density was highest in the oak wood (93 birds/ 10 ha) and lowest in a heathland site, the four and one‐year‐old eucalypt stands (26,13, and seven bird/10 ha respectively). The wren was the most widespread and dominant species occurring in all study areas except the one‐year‐old eucalypt stand. Mean bird species diversity for the four eucalypt stands was significantly lower than mean bird species diversity for the other wooded habitats. The avian communities of the heathlands, maritime pine and eucalypt plantations, in contrast to the oak wood and farmland, show an excessively high dominance of one species. Using avian dominance as a biological index of habitat perturbation suggests that over half the landscape (4000 km2) in northwestern Galicia is suffering from chronic stress. The newest stress to the avifauna in a long history of land exploitation by man is the importation and cultivation on grand scale of eucalypts. Balancing this tendency, traditional, small‐scale farming on the mountainous terrain leads to the development of many tiny parcels whose average size is 0.28 ha; this in turn creates much ‘edge’ in hedgerow which serves to maintain a relatively rich avian species