Dispersal of a Neotropical Nutmeg (Virola sebifera) by Birds

Al•ST•CT.--Feedingassemblages of birds were observed at a Panamanian population of Virola sebifera (Myristicaceae) in order to test the hypothesis that plants producing especially nutritious fruits in limited supply should be efficiently dispersed by a small set of obligate frugivores.Virola sebifera produces an encapsulated arillate seed that is swallowed by birds shortly after dehiscence.The aril (54% lipid, 7% protein, 8% usable carbohydrate) is retained; the seed is regurgitated intact within 10-30 min.The plant produces 1-96 (Yc = 24) ripe arillate seeds each day, of which 40-89% (Yc = 76%) are taken within a few hours of dawn.The visitor assemblage consists of six resident frugivores.Three [Chestnut-mandibled Toucan (Ramphastos swainsonii), Keel-billed Toucans (R. sulfuratus), and Masked Tityra (Tityra semifasciata)] are "regulars," likely to visit all trees; three [Slaty-tailed Trogon (2•rogon massena), Rufous Motmot (Baryphthengus martii), and Collared Aracari (Pteroglossus torquatus) are common throughout the Barro Colorado Forest but do not consistently use Virola sebifera.The Chestnut-mandibled Toucan is responsible for 43% of the seeds removed by birds, although it is also responsible for more seed waste (regurgitation under the tree crown) than other visitors.Rapid depletion of available fruits each morning and active defense of the crowns by toucans suggest a limited and preferred food resource for "regulars" in the assemblage.A review of recent work indicates that the assemblage visiting Virola sebifera is similar to that frequenting its larger congener (V.surinamensis) but is far smaller and more specialized than those visiting other fruiting trees in the same forest.