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Avian Ecology and Conservation in an Urbanizing World

The effects of human disturbance in urban parks of Madrid (Spain) on bird tolerance were studied to derive recommendations for urban park planning. We intended to determine (1) how habitat structure influenced flush distances, (2) whether flush distance increased with body-size, and (3) whether flush distances varied with the amount of people visiting the park. In four city parks in Madrid with different levels of human visitation and habitat structure, we recorded flush distances of four bird species of different sizes (overall body length: Passer domesticus, 15 cm; Turdus merula, 24-25 cm; Columba palumbus, 40-42 cm; Pica pica, 44-48 cm). Humans approached individual birds when they were foraging on the ground. Habitat structure (shrub cover, shrub and tree height) influenced flush distances of the four species. After controlling for the effects of different microhabitat use, averaged flush distances varied significantly among species; large species were less tolerant of human disturbance than small ones. Birds were more tolerant of our intrusions in parks with more human visitors. To enhance the suitability of urban parks for bird species, the following recommendations may be considered: (a) flush distances could be a first indicator of appropriate set-back distances (minimal distance that a pedestrian may approach a bird) for pathways, (b) flush distances of large bird species could be used to determine minimum area requirements of resource patches separated by pathways, (c) habitat complexity could increase the availability of escape cover for native bird species, and (d) highly variable visitation rates may be less harmful in popular parks, because bird tolerance to human disturbance appears to increase with the overall amount of visitors per park.