Inconspicuous, Sociable, Waterbirds… Nankeen Night-Herons

By Keith Hutton on February 12, 2016 in Other

Nankeen Night-Herons are native Australian birds that are largely nocturnal or crepuscular. They usually roost during the day in groups in leafy trees growing near water. In the Sydney region, where they associate in small parties in suitable wetland habitat, they are uncommon and inconspicuous. Sociable, nomadic and dispersive in response to rainfall, they aggregate into larger groups to breed in colonies, often near egrets in trees over water, when and where conditions are favourable.

Adults are unmistakeable. They stand with a stooped appearance: handsome, stocky, medium size water birds with long, powerful, olive-green bills. They appear very neat and tidy, aloof, with rich distinctive cinnamon upperparts, an obvious black crown, white buff underparts, yellow feet and relatively short yellow legs; their eyes are bright yellow. Sexes are alike but young birds are very different: relatively plain, heavily spotted and streaked white and brown.

Nankeen Night-Herons occur in wetlands throughout Australia, in the shallow margins of rivers, mangrove-lined estuaries, ornamental ponds, offshore islands and floodwaters, but are not common in Tasmania. They are also in Indonesia, New Guinea, the Solomon Islands, New Caledonia, the southwest Pacific, and turn up as vagrants in New Zealand.

In the Eastern Suburbs they were formerly seen regularly over many years in Centennial Parklands, but now they occur less frequently. Nevertheless, they were recorded in the Centennial Parklands Bird Spotting Challenge recently, and there were two seen by the editor of this publication in December, just after sunset, on a small island in the Duck Pond, near Willow Pond.

They feed alone or in large flocks and eat mainly fish, frogs, freshwater crayfish and aquatic insects, but are versatile, opportunistic predators. For example, they are known to attend mouse plagues, and feed on beaches when young sea-turtles hatch and scramble down to the sea after leaving the relative safety of their nests in the sand; they also take eggs and chicks where colonies of water birds breed, and scavenge among garbage. Nankeen Night-Herons usually feed in shallow water or on adjacent land, in late evening and at night, but also in daylight when breeding. When hunting they stand and wait in erect or crouched posture, or walk slowly until food is located. They will also drop on to aquatic prey from low branches over water, and actively pursue terrestrial items overland.

Despite increased awareness and consequent improvements in recent years, there still remain potential threats for water birds related to pollution, water quality, drainage of wetlands and interruption of river flows that disrupt breeding activity. However, provided that an adequate network of wetland habitats is maintained, the future for night-herons will be assured. They remain common in suitable habitats in Australia, despite significant regional variation in numbers recorded late last century, and an apparent decrease in overall numbers nationally over the same period. The conservation status of Nankeen Night-Herons is currently considered to be of least concern.