Responses of Venezuelan understory birds to selective logging, enrichment strips, and vine cutting


D Mason

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Structure and microhabitat conditions of low light and high humidity of the understory are greatly altered by logging, while the canopy microclimate remains much the same, and may even expand as logging opens spaces and allows canopy species to forage closer to the ground (Wong 1985). Many canopy birds are also adapted for foraging on patchy resources over large areas. They may be better able to exploit logged landscapes, which area mosaic of logged and unloggged. Some understory birds will not cross even small gaps (Karr 1982, Bierregaard and Lovejoy 1989). Most understory species were insectivores, and most declined in abundance after logging. Bark foraging birds (e.g. woodcreepers) tended to be less common in disturbed forests. Foliage-gleaning insectivores (like antbirds) also declined. Five to six years after logging, the understory veg was twice as dense as that of primary forest and hte bird assemblages were sign different. Understory FOREST STRUCTURE CORRELATED BEST WITH CHANGES IN BIRD COMMUNITIES, AND INSECTIVOROUS BIRDS, WHICH DOMINATE THE UNDERSTORY, ARE KNWON TO BE VERY SPECIALIZED IN THE WAYS THAT THEY FORAGE. Changes may also occur in the types of insect prey available (Holloway et al. 1992). Forestry disturbance may favor generalists (eg frugivores) over specialists. Very selective logging coupled with a treatment to cut woody vines did not greatly affect the understory avifauna.