A novel feeding mechanism: Sunbirds drink nectar via intralingual suction

Nectarivory has independently evolved many times among birds, yet little is known about the diversity of feeding mechanisms that enable specialized taxa to efficiently collect this energyrich resource. Multiple avian groups have converged on evolving elongated bills and tube-like tongues adapted for nectar extraction. Old World sunbirds (family Nectariniidae) stand out as having the greatest degree of convergence in bill and tongue morphology with the well-studied and highly-specialized New World hummingbirds (family Trochilidae) which fill their tongues via elastic filling. However, using museum specimens, high-speed video, and fluid modeling, we show that sunbirds use a previously undescribed and unique drinking mechanism not found in any other animal: intralingual suction through the inside of hollow tubular tongues, a remarkable feat for animals without lips or cheeks.