Loss of insectivorous birds along a gradient of human impact in Amazonia Original Research Article

Birds were surveyed within four zones defined along a gradient of decreasing impact by the petroleum industry and small-scale agriculture in the moist tropical forest of the Cuyabeno Wildlife Production Reserve in northeastern Ecuador. A total of 12 3-day surveys were conducted at nine sites, divided among the four zones, which consisted of a coffee plantation on the edge of a large deforested area, and three primary forest zones at approximately 0, 1500, and 3200 m from the deforested area (0, 200, and 1000 m from small clearings; 200, 2000, and > 3500 m from roads). All sites were located on the same types of soil and terrain, and the vegetation of all forested sites was physiognomically similar. The most outstanding difference in bird species composition across zones was the reduced number of insectivores in areas of greater human impact (p=0·03). Interior forest insectivore species were significantly more likely to be absent from impacted forests (and non-forest habitats) than were non-insectivores (p=0·000004), and this tendency was also present in the results of other studies of tropical forest birds. These results underscore the need to take insectivores, as well as other particularly sensitive groups, into special consideration within conservation strategies if intact faunas are to be preserved.