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The feeding ecology of the Wrybill (Anarhynchus frontalis) was compared between two sites – a flood-prone riverbed and a stable riverbed. Larvae of aquatic insects, particularly mayfly (Deleatidium spp.), were the main prey of Wrybills, which captured them by a variety of methods. The sideways-bent bill was useful in capturing insects from the under-surface of stones where they would normally have been inaccessible to birds with shorter, straight, or even up-curved bills. The evolutionary significance of the bent bill is discussed with reference to climatic trends during and since the Pleistocene period. During floods, aquatic prey was relatively unavailable to Wrybills, causing them to switch to riparian foraging.