Feeding ecology of green catbirds (Ailuroedus crassirostris) in subtropical rainforests of south-eastern Queensland.

Abstract

Foraging data for green catbirds were collected over an 8-year period in lowland (dry) and upland (wet) subtropical rainforests of the Jimna and Conondale Ranges. The fruits of 104 species of trees, palms and vines comprised the bulk of the diet. Catbirds foraged the fruits of a similar number of species (56) in lowland forest as in upland forest (60). Lowland forest was distinctive, however, in that almost 77% of the food plants occurring in upland forest were rare or absent in lowland forest. Catbirds also foraged flowers, various plant material, insects and millipedes, and these were also significant components of the diet during spring and summer. Different species of asynchronous fruiting figs (Ficus spp.) occurred in lowland and upland forest, and these were the most important foods in each forest type. In lowland forest, catbirds seldom ventured beyond their home ranges (average size 1.9+/-O.2 ha) to forage, and bred from December to March when figs were the only reliable fruit that figured prominently in the diet. Insects also appeared to be an important (perhaps essential) component of the nestling diet during this period. Long-term (5-10 years) data on the fruiting phenology of 94 of the food plants enabled the relationship between the fruiting reliability of food plants and their importance in the diet to be evaluated. Availability of most (79% in lowland forest, 77% in upland forest) species of fruit was irregular and foraging by catbirds was therefore mostly opportunistic.