Fig. 5. Bending zones in the upper bill elements of the purple sandpiper Calidris maratima. Relative thickness of the dorsal bar (A) and ventral bar (B) vs the distance from the bill tip. Lines are Lowess fits indicating average relative thickness. In this and subsequent figures, vertical broken lines where shown indicate morphological characters of the bill: (a) caudal border of the rostrum maxillae, (b) rostral point of the rostrum basisphenoideus, (c) position of the lateral bar (b and c not present in this species). Arrows indicate the position of the bending zones as observed during experimental manipulation of the upper bill or from kinematical analysis.