FOOD RESOURCE EXPLOITATION STRATEGIES OF TWO REEDBED SPECIALIST PASSERINES: REED PARROTBILL AND ORIENTAL REED WARBLER

We studied the nestling diet of two reedbed specialist passerines, Reed Parrotbill (Paradoxornis heudei) and Oriental Reed Warbler (Acrocephalus orientalis) in a tidal reedbed in the Changjiang River Estuary, China. Reed Parrotbills delivered mainly Homoptera, Diptera, and Leptidoptera to their nestlings, and Oriental Reed Warblers delivered mainly Diptera, Hymenoptera, Araneida, and Lepidoptera to their nestlings. More than 98% of the diet of nestling Reed Parrotbills consisted of wingless items and >97% consisted of concealed items, indicating that Reed Parrotbills are limited in their ability to catch winged prey capable of strong flight and rather they retrieve prey from within reed shoots using their large and strong beaks. About 85% of the diet of nestling Oriental Reed Warblers consisted of winged items and >99% consisted of exposed items, indicating that Oriental Reed Warblers are limited in their ability to retrieve prey from within reed shoots and depend on their flight ability to catch prey capable of flight. Oriental Reed Warblers had significantly more taxonomic categories of prey in their diet, significantly wider diet niche, and significantly higher diversity in nestling diet than Reed Parrotbills. Our study demonstrates that although these two species breed sympatrically in reedbeds as reedbed specialist, Reed Parrotbills and Oriental Reed Warblers use different strategies in their exploitation of food resources.