While some species of plants can offer seed-disseminators fruit rewards, studies have shown
that the density of frugivorous birds increases with the structural complexity of the vegetation alone
(McDonnell and Stiles, 1983). Robinson and Handel’s (1993) studies of experimental plantations
showed a positive correlation between vegetation height and the density of new seedling recruits,
suggesting that fruit-eating birds are drawn towards the taller plants in early successional habitats.
This supports the finding, based on a study conducted in the northeastern U.S., that frugivorous birds
using early successional fields prefer perches that are taller than the surrounding vegetation
(McDonnell, 1986).