Successful, Aquatic, Snakebirds… Australasian DartersAustralasian Darters are large water birds that superficially resemble cormorants and shags, and have a preference for still inland swamps, lagoons and creeks. They are common breeding residents in the Sydney region that are seen regularly in suitable habitats. They breed in small numbers in Centennial Park in the warmer months of the year but are much less numerous than cormorants in the Eastern Suburbs.
A darter is a large, spectacular, long-necked bird that soars to great heights on broad flat wings with its wedge-shaped tail fanned – like a flying cross. They are usually seen alone or in pairs. Plumage is not water-repellent so after swimming darters hold their wings out to dry when perched, like the cormorants they often associate with. When swimming and hunting a darter immerses itself in water with its body submerged and only its head and neck above the surface, when it resembles a swimming snake. Male birds appear glossy black, female birds dark grey, and both have a variable white stripe from the eye to behind the neck. Their wings are iridescent with cream streaks and they have long rounded tails, short legs and webbed feet; bills resemble stilettos – needle-tipped, slender and straight.
Australasian Darters can be found in suitable habitat throughout mainland Australia, Torres Strait Islands, New Guinea and parts of Indonesia. Open water and places to perch, rest and dry their wings are essential. Large shallow waters, rivers, lakes, swamps, reservoirs, tidal inlets, and harbours meet their requirements and most breeding takes place inland and in sheltered estuaries.
Darters usually fish alone in calm water; they are stealthy hunters that do not swim after food in active pursuit like cormorants do. They sink gradually, submerge inconspicuously leaving barely a ripple, and stalk prey underwater slowly and deliberately, waiting until close enough to strike. The neck is held in an s-shape, then the head darts forward with lightning speed and the target is speared with the sharp, pointed bill. The bird then surfaces and the prey is flicked off the bill on to the water, quickly retrieved then swallowed headfirst. Speared fish are occasionally tossed into the air and caught before hitting the water. Baby turtles, yabbies and aquatic insects are also eaten. Smaller items are swallowed underwater and bigger fish carried to a tree or log where they may take up to twenty minutes to be swallowed. Other small prey such as insects and spiders are picked from the water using their bill-like forceps.
In NSW darters feed extensively on carp and redfin that have been spectacularly prolific since introduction from Europe. This opportunism may be responsible in some part for recent increased observations of darters. However, a proposal to eradicate these exotic fish may reduce available food and change the conservation status for darters in the future, despite them thriving in the current conditions.