Australasian Darter

Darter hanging out to dry, Mulwarree Chain of Ponds.

Darter hanging out to dry, Mulwarree Chain of Ponds.

 

The Australasian Darter Anhinga novaehollandiae or Snake Bird is a species that is relatively uncommon in the Goulburn district. It is also particularly interesting for a number of good reasons.

Many birds have evolved a fish eating diet and the Darter is a prime example. But unlike other diving birds, the darter seems to have borrowed a few features from unrelated species and glued them together to make a unique organism. Like grebes, it swims rapidly underwater for its food; like cormorants it has feathers with low oil content to enable it to stay under longer; like egrets and herons it has a long stabbing beak and a spring-jointed neck that, when triggered, enables it to stab fish at lightning speed.

Non-breeding male darter. Note the large, heavily webbed feet.

Non-breeding male darter. Note the large, heavily webbed feet.

Like grebes it has small legs placed well to the rear, making it clumsy on land. But unlike grebes it has very large webbed feet to propel it through the water. Its method of stabbing prey is like herons and egrets, but unlike them it can use the mechanism while swimming after its prey. Like cormorants it swims low in the water, but unlike them it swims so low that only its head and neck appear above the water, so it looks a lot like a snake when seen from a distance. Of course no snake actually swims with such a long part of its body out of the water, nor does any snake have a stiletto-like snout.

A young male darter. Unlike females the underside of its neck is black.

A young male darter. Unlike females the underside of its neck is black.

The sexes of some of the birds discussed in this website are monomorphic (males look pretty much just like females), while others are dimorphic (males and females are easy to tell apart). Darters go a little further. Adult males are black with white streaks on their faces. When breeding they gain rich chestnut marks on their necks and long silvery-edged feathers on the back of their wings, as can be seen in the photo at the top of this page. Females are paler, or more greyish, than males and their breasts and the front of their necks are white. Young birds that can fly are paler again than the females. Young males, as they get older, look like darker females, but the whole of their neck is black.

Curious bowing posture of a darter in the Goulburn wetlands.

Curious bowing posture of a darter in the Goulburn wetlands.

Like cormorants, darters’ low oil feathers get soaked after a while in the water. This weighs them down and can stop them flying away if they need to. As a result, as soon as darters get out of the water they hang themselves out to dry by holding their wings out from their body in the sun (if it is a sunny day). When not drying themselves, darters tend to sit still in an upright, slim posture that probably helps them stay unnoticed by predators. In the Goulburn wetlands a male darter was seen to lean forwards, lift its wings and hold that posture for several minutes. Whether it was an odd form of feather drying or a specific display is not clear. There were no other darters or apparent threats in the vicinity at the time.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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