Flock of Plumed Whistling Ducks (Tree Ducks) Dendrocygna eytoni whistle and posture in group communication at sunset beside a Gulf lowland billabong, their daytime roost, in the Gilbert-Smithburne River Delta, Gulf of Carpentaria, Queensland, Australia, before flying off at dusk to their night time feeding areas on the moist fringes of drying floodplain wetlands.