Abstract

We examined the feeding behavior and nutritional ecology of one of the smallest species of avian herbivores (ca. 44 g), the Rufous-tailed Plantcutter Phytotoma rara (Phytotomidae). This species inhabits forests and scrublands, as well as crop fields and orchards in central Chile. Field and laboratory data revealed that P. rara is a herbivorous bird with marked preferences for leaves in comparison to fruits and insects. When P. rara eats a highly diluted plant material (such as lettuce), a shorter digesta retention time and a lower apparent digestibility was observed in comparison to a high-quality diet. Wet-mass daily intake of plant material was 5.4 times body mass, two times higher compared with the high-quality diet. The larger proportion of water and refractory materials in lettuce diet may explain the variation in ingestion rates. Feeding bouts were longer with lettuce diet, because birds spent more time handling and chewing previous ingesta. Chewing may increase overall digestibility through physical breakdown of cell walls, making available the highly digestible cell contents. These strategies may allow P. rara to maintain body mass balance when feeding on highly diluted plant material.