Responses of Venezuelan Understory Birds to Selective Logging, Enrichment Strips, and Vine Cutting

Abstract

This paper examines the impact of selective logging and two silvicultural treatments (enrichment strips and vine cutting) on understory birds in southern Venezuela. Birds were sampled using mist nets from 1992-93. Assemblages in each forest type were compared with reference plots in primary forest. While selective logging significantly affected understory bird assemblages, the effects were even greater when enrichment strips (linear plantations) were created following harvesting. Bird assemblages changed in proportion to the magnitude of the forestry disturbances. With increasing disturbance, nectarivores increased in abundance while the responses of frugivores were mixed. Insectivores dominated the understory avifauna and generally declined in abundance. The most diverse family of understory birds, the antbirds (Formicariidae), was typical of insectivores. Of the 22 species which occur in primary forest, a few (two spp.) became abundant following selective logging, but most (16 spp.) declined and several (four spp.) were not recorded in logged forest. Compositional changes and the frequency of extirpations were even greater following the creation of enrichment strips. Eliminating this silvicultural practice, or replacing it with a less damaging alternative, would better conserve the forest avifauna. Cutting vines, which did not greatly alter the structure of the forest understory, had little effect on understory birds.