Interactions Between Birds and Fruits in a Northern Florida Hammock Community

This paper examines interactions between 22 bird species and 45 species of bird—dispersed plants in a northern Florida hammock community from April 1982 to May 1984. Seasonal patterns of frugivore availability and fruiting phenology were determined and compared. Frugivore species diversity and abundance were highest during the fall and winter months and lowest in the spring and summer. Increases in frugivore numbers and diversity were attributed to the presence of migrant thrushes in the early fall and of overwintering frugivores in the late fall and winter. The timing of fruiting for the plant species studied over an annual period showed a significant correlation with frugivore diversity and abundance. Spring and summer months showed the lowest number of fruiting species and fall and winter the highest, with a peak of 28 species in fruit in December. Fruiting patterns fell into four seasonal groups: summer, fall, fall—winter, and winter fruiting. Nine species showed summer fruiting, bearing ripe fruit between early spring and late summer. Summer—fruiting species were uncommon in the community and typically occurred in disturbed areas. These species appeared to use both mammals and birds for seed dispersal. The 12 fall—fruiting species ripened fruit at the peak of frugivore migration through northern Florida. Fall—fruiting species were common or abundant in the community and dependent primarily on migrant thrushes for seed dispersal. The 20 fall—winter fruiting species produced highly persistent fruits that were available to migrant frugivores through fall and winter. The four winter—fruiting species matured fruit in December and depended on overwintering birds for seed dispersal. No clear seasonal trend were evident for ripening synchrony patterns. The bird—fruit dispersal system of the lower temperate latitude hammock community shows similarities in fruiting patterns to middle latitudes of North America. Mild winters, the presence of evergreen species, and large populations of overwintering frugivores, however, have made winter fruiting more prevalent at lower latitudes than middle latitudes.