Depth of vane in barn owl and pigeon wing feathers. Normalised depth of the outer and inner vane of remiges (A, B) and coverts (C, D) in the barn owl (A, C) and the pigeon (B, D). The colours indicate different feathers. Their position is presented at the wing. The depth was measured at right angles to the rachis and was then normalised with respect to the whole length of vane.