Baer's pochard (Aythya baeri) smart courtship; the males regularly perform a kinked-neck call and regularly show head-throws in this clip, tilting their bills to the side of the nearest female. Females sometimes perform a head-throw and kinked-neck call too (Johnsgard, 1965) but I have not observed this behaviour in females yet. Females do, however, frequently "preen-behind-the-wing" to males.
