Date of Award

1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

James V. Remsen, Jr

Abstract

By spot-mapping territories of lowland forest birds in southeastern Peru, 19 "bamboo specialists" were documented to be restricted to thickets of bamboo (Guadua weberbaueri). Six specialists are restricted to thickets throughout their entire geographic range (obligate bamboo users); seven specialists may use other habitats sparingly away from southeastern Peru (near-obligate bamboo users); the remaining six species are frequent users of habitats lacking bamboo in area besides southeastern Peru (facultative bamboo users). The 19 specialists, all insectivorous, were classified into five guilds based on foraging maneuver and substrate preferences: four sallying tyrannid species; four arboreal antbirds; four stem-searching specialists; four dead-leaf-searching specialists; and three species that foraged low in bamboo thickets. I investigated niche-partitioning within the guilds along dimensions of habitat use and foraging behavior. Aside from pairs of specialists in the antbird and dead-leaf guilds, little niche-partitioning was found among the three structurally different types of bamboo thickets present in the study area (bluff-top, floodplain forest, and early successional bamboo). The specialists showed more partitioning in foraging behavior, particularly among the perch, attack and substrate variables. Except for the flycatcher guild, specialists showed high overlap among the continuous foraging variables (height, distance to canopy, perch size, perch foliage density), reflecting the small range of these variables in structurally uniform thickets. A distinction was made between species specializing only on the unique structure of bamboo thickets (habitat specialists) and those that showed signs of further specialization on unique bamboo substrates or prey bases available in bamboo. The probable habitat specialists included only one obligate specialist; all others were facultative or near-obligate specialists. Five of six obligate and two near-obligate specialists showed indications of substrate specialization. However, only one specialist, Simoxenops ucayalae, showed morphological adaptations, which may be related to this species' unique foraging behavior. Using specialist densities from spot-mapping results and habitat areas from a satellite image of southeastern Peru and northern Bolivia, I made rough estimates of the regional population sizes of each specialist and discuss conservation implications of encroaching development in the area.

Pages

141

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