PARENT SESSION
Oral Session #36: Animal Community Ecology.
Presiding: S. Simonson
Tuesday, August 6. 8:00 AM to 11:30 AM. Mesquite Room, Radisson.
Factors influencing the density of birds on small islands in Lago Guri, Venezuela.
FEELEY, KENNETH*,1, 1 Duke University, Durham, NC, USA
ABSTRACT- The factors that influence the densities of organisms in fragmented habitats are complex and poorly understood. In the summer 2000, I censused the populations of forest-interior birds nesting on over 30 land-bridge islands located in Lago Guri Venezuela. These censuses revealed small islands (<2.5 ha) to support over twice the density of breeding birds as found on larger landmasses (>100 ha). In an attempt to understand this pattern, I investigated the role a large number of different environmental and ecological variables using multiple regression techniques. This analysis led to the surprising result that bird densities are strongly positively correlated (p<0.0005, r2=0.69) with the density of relict populations of howler monkeys (Alouatta seniculus) trapped on the islands. This relationship is believed to be the result of a series of complex indirect interactions. High levels of herbivory are hypothesized to cause changes in the plant communities and rates of nutrient cycling. In turn, these changes may favor increased insect abundances and account for the observed bird densities. Indirect and diffuse interactions must be taken into account when investigating community structure.
KEY WORDS: ragmentation, avian densities, indirect interactions, Lago Guri Venezuela