Zimmer's Woodcreeper is so similar to Straight-billed Woodcreeper (D. picus) that it is almost impossible to tell them apart in the field. However, we were lucky in that we had a recording of Zimmer's voice which allowed us to make a positive identification. One of the principle features (shared with the Straight-billed) is the bill being straight and ivory coloured but with a pinkish tinge.