Courtship display in blue-capped cordon-bleus.
(a) When blue-capped cordon-bleus perform courtship display, (b) they simultaneous bob and step and (c) sing at certain times. Bobbing (shaded bars) with multiple steps (white bars) is repeated often and usually singing occurs several times. White and shaded arrows in (b) correspond with the colour of bars in (c). Note the number of steps in (c) involved in each bobbing action.