Feeding behavior and assimilation efficiency of the Rufous-tailed Plantcutter: A small avian herbivore

We examined the feeding behavior and nutritional ecology of one of the smal lest species of avian herbivores (ca. 44 g), the Rufous-tailed Plant-cutter Phytotoma rara (Phytotomidae). This species inhabits forests and scrubland s, as well as crop fields and orchards in central Chile. Field and laborato ry 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-qu ality 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 proporti on of water and refractory materials in lettuce diet may explain the variat ion in ingestion rates. Feeding bouts were longer with lettuce diet, becaus e birds spent more time handling and chewing previous ingesta. Chewing may increase overall digestibility through physical breakdown of cell walls, ma king available the highly digestible cell contents. These strategies may al low P. rara to maintain body mass balance when feeding on highly diluted pl ant material.