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Pre-dispersal Seed Predation by a Granivorous Bird, the Masked Grosbeak (Eophona personata), in Two Bird-dispersed Ulmaceae Species

Author(s): Tetsuro Yoshikawa | Kihachiro Kikuzawa

Journal: Journal of Ecology and Field Biology
ISSN 1975-020X

Volume: 32;
Issue: 3;
Start page: 137;
Date: 2009;
Original page

Keywords: Fleshy fruit | Granivory | Plant-animal interaction | Plant phenology | Seed dispersal

Pre-dispersal seed predation by a granivorous bird, the masked grosbeak (Eophona personata,Fringillidae), was investigated in two bird-dispersed trees, Celtis sinensis and Aphananthe aspera (Ulmaceae).The objectives of this study were to 1) measure direct damage of predation by grosbeaks on plant crops, 2)reveal the temporal pattern of predation within each tree species and its causal factors, and 3) test whetherforaging grosbeaks hinder foraging of frugivorous birds, thereby indirectly impacting the reproduction of both treespecies. A substantial amount of fruit and seed crop was consumed by grosbeaks (24.3% in Celtis; 55.5% inAphananthe), and only 17.7% (Celtis) and 16.7% (Aphananthe) were removed by frugivorous birds. At the studysite, the grosbeak population size fluctuated greatly during the fruiting seasons of both plant species. As forCeltis, predated seed density also fluctuated temporally, and the local population size of grosbeaks was responsiblefor predated seed density. In Aphananthe, predation was not fully explained by grosbeak populationsor plant phenology, but its peak coincided with that of grosbeak population. These results suggest that predispersalseed predation by granivorous birds can have large negative impacts on the bird-dispersed plants.Changes in local population size of granivorous birds can influence predatation and can affect reproductivesuccess of the bird-dispersed plants available to the birds.
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