Relationships between bird-dispersed plants and avian fruit consumers with different feeding strategies in Japan

We examined the interactions between bird-dispersed plants and fruit-consuming birds with various feeding strategies, by reviewing the plant species consumed by 14 bird species in Japan with four feeding types: gulpers (five species), grinders (four species), crushers (four species), and peckers (one species). Our literature review provided information on the plant species consumed by the birds in Japan and the morphological traits of the fruits: fruit volume, seed mass and number, pulp type (fleshy, dry, or arillate), and plant height (tall, medium, or small). Using these data, we examined the diversity of plant species consumed by each bird and the fruit morphological traits that affected fruit selection. The five gulpers consumed fruits from the largest number of plants, followed by the four grinders, the four crushers, and the one pecker. The gulpers and grinders consumed a wider variety of fruits than were consumed by the crushers and the pecker. Logistic regression analysis revealed that some crushers and the pecker preferred plants with dry or arillate pulp around the seeds. Our results suggest that a frugivorous bird's feeding strategies, and particularly its fruit-handling behaviors and the fruit parts it ingests, influence the diversity of plants it consumes. The crushers and the pecker, which feed exclusively on seeds, require more effort and time to consume this type of food, and this might cause a strong preference for specific fruit traits and thus, consumption of a lower diversity of plant species.