THE FOOD AND FEEDING APPARATUS OF THE BLUE DUCK HYMENOLAIMUS

This paper describes a preliminary study of the feeding behaviour of the territorial Blue Duck. The bird is unusual in possessing lateral bill flaps and, in a number of head and skull characters, differs from a typical dabbling duck. Herbst's corpuscles are absent from the outer 60% of the width of the flaps and this is thought to indicate that any tactile function is subsidiary. It is tentatively suggested that an additional function is protective, and that the flaps cushion the jaw edges during vigorous food searching beneath stones on rocky stream bottoms. Food taken in summer was analysed from remains in droppings and from gut contents and was found to consist of aquatic insects, principally case-living and free-living caddis larvae, and algae. Some short-term variation in the diet was noted. It is suggested, also tentatively, that the decline in Blue Duck numbers since the 19th century has been associated with the introduction of trout which are potentially direct food competitors. Further ecological research on this unique species is required.