Bird activity and seed dispersal in two neotropical trees: Guarea macrophylla and Trichilia quadrijuga
Prado, Fred A.
In Manu National Park, Peru, l investigated bird activity on and seed dispersal of two sympatric neotropical rain forest trees: Guarea macrophylla and Trichilia quadrijuga. Of 24 bird species that consumed Guarea fruits, only four (Catharus ustulatus, Myoidynastes luteiventris, Pipra coronata, and P. fasciicauda) consistently visited and dispersed its seeds. Of three bird species that consumed Trichilia fruits, two (P. fasciicauda and P. chloromeros) regularly visited and dispersed its seeds. As Catharus and Myiodynastes are northern migrants, their consumption of Guarea fruit might partially account for the distribution of this plant in Amazonian South America. I also investigated the time of visit for each bird, the length of the visit, whether the bird perched on the fruiting tree, its method of plucking a pulp unit (aril plus seed), number of pulp units ingested per visit, method of ingestion, and whether seeds were dropped under the parent tree or carried away from the canopy after ingestion. I measured and weighed pulp units and seeds of G. macrophylla and T. quadrijuga and compared these measurements with bill dimensions of bird species to determine if the size of the pulp unit or seed could be correlated with any aspect of bird feeding behavior or seed dispersal. Variance in the time spent at fruiting trees across and within bird species was high. Most bird activity occurred between 700 h and 1000 h. With few exceptions, all visiting birds perched in the observed tree and either removed fruit in flight or from a nearby perch. The number of ingested pulp units per visit ranged from 0 to six depending on the bird. Few seeds were dropped under the parent tree. The mean measurements for Guarea pulp units were l 0.4 mm long, 7.2 mm wide, and 5.6 mm deep; whereas, Trichilia pulp units were 12.7 mm long and 5.9 mm in diameter. Pulp units of both tree species had a mean weight of 0.27 g. The observations of bird activities did not support the idea of tight coevolution between these Meliaceae plants and their seed dispersers since the fruits were small enough to be ingested by many species of birds and because the most reliable dispersers are not uniquely frugivorous.
Seed dispersal, Neotropical trees, Guarea, Trichilia
Prado, F. A. (1999). <i>Bird activity and seed dispersal in two neotropical trees: Guarea macrophylla and Trichilia quadrijuga</i> (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.