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470117 
Journal Article 
Habitat fragmentation and effects of herbivore (howler monkey) abundances on bird species richness 
Feeley, KJ; Terborgh, JW 
2006 
Yes 
Ecology
ISSN: 0012-9658
EISSN: 1920-2005 
87 
1 
144-150 
English 
Habitat fragmentation can alter herbivore abundances, potentially causing changes in the plant community that can propagate through the food web and eventually influence other important taxonomic groups such as birds. Here we test the relationship between the density of red howler monkeys (Alouatta seniculus) and bird species richness on a large set of recently isolated land-bridge islands in Lago Guri, Venezuela (n = 29 islands). Several of these islands host relict populations of howler monkeys at densities up to more than 30 times greater than those on the mainland. These "hyperabundant" herbivores previously have been shown to have a strong positive influence on aboveground plant productivity. We predicted that this should lead to a positive, indirect effect of howler monkey density on bird species richness. After accounting for passive sampling (the tendency for species richness to be positively associated with island area, regardless of differences in habitat quality) we found a significant positive correlation between howler monkey density and bird species richness. A path analysis incorporating data on tree growth rates from a subset of islands (n = 9) supported the hypothesis that the effect of howler monkeys on the, resident bird communities is indirect and is mediated through changes in plant productivity and habitat quality. These results highlight the potential for disparate taxonomic groups to be related through indirect interactions and trophic cascades. 
Alouatta seniculus; bird species richness; faunal relaxation; grazing; optimization; habitat fragmentation; herbivory; indirect effects; Lago; Guri; Venezuela; passive sampling; red howler monkey; species-area; relationship; tropical dry forest; amazonian forest fragments; land-bridge islands; caroni river basin; tropical forest; soil nutrients; french-guiana; diversity; communities; patterns; guri