Influence of matrix habitats on the occurrence of insectivorous bird species in Amazonian forest framents

The influence of matrix habitats on the occurrence of seven understory insectivorous bird species in forest fragments was examined at the Biological Dynamics of Forest Fragments Project, Manaus. Amazonia. Playback techniques were used to detect individuals in the continuous primary forest, fragments of 1, 10 and 100 ha, and in two matrix habitat of secondary forest dominated by Vismia spp. and Cecropia spp. Sampling points in secondary forest areas were distributed at 50, 250 and 500 in from the continuous forest. Using G-tests of frequency distribution, species occurrences were compared in the following ways: (a) continuous forest vs. fragments; (b) continuous forest vs. second growth forest; (c) in second growth at different distance, from continuous forest. Species were divided into three categories according to their sensitivity to the fragmentation process. Highly sensitive species (Cyphorhinus arada, Hylophilus ochraceiceps and Thamnomanes ardesiacus) did not occur in small fragments or in matrix habitats. Moderately sensitive species (Formicarius colma and T. caesius) occurred in small fragments and utilized infrequently matrix habitats. Positively affected species (Percnostola rufifrons and Hypocnemis canator) were frequently detected in small fragments and all matrix habitats. Distances from the continuous forest did not influence the frequency of species occurrences in the secondary forest areas. Species were more frequent in small fragments surrounded by Cecropia spp. than by Vismia spp. Our results support the idea that the maintenance of species in small fragments may depend on their ability to use the matrix, and that increasing the permeability of the matrix may be an option to lessen the effects of forest fragmentation. (C) 2004 Elsevier Ltd. All rights reserved.