Abstract
To elucidate sexual differences in the foraging behavior of passerines, we investigated the foraging height and behavior of the Narcissus Flycatcher Ficedula narcissina in relation to vegetational types in primary forest on Mt Fuji, Japan, in 2009 and 2010. Female flycatchers foraged at higher levels than males in evergreen coniferous forest, whereas they foraged at lower levels than males in broadleaf deciduous forest. Females foraged around their nests, and therefore their foraging height was linked to nest height. Female foraging height differed between forest types. These results suggest that female foraging height is flexible in relation to their environment. Males foraged near their song posts, thus their foraging height correlates with the height of their song posts; as a consequence there was no difference in their foraging height between differing forest types. In 2009, in both forest types, female flycatchers often foraged by sally-hovering. Sally-hovering was observed from mid-May to June, coinciding with their incubation and nestling periods. Female flycatchers build nests and incubate alone, and forage for arthropod prey around their nests; as a result female foraging time may be shorter than that of males. Sally-hovering is an avian foraging technique adapted to capturing insect prey dwelling among leaves, and it may be particularly suitable for foraging in narrow spaces when foraging time is limited. In 2010, no sexual differences in foraging behavior were found, suggesting that in addition to vegetation type, annual variations in climate and prey abundance also affect foraging behavior.
