Swan studies hatching surprise results
RECENTLY I was told of a pair of black swans that had nested near Moolap.
Sadly one of the pair, presumed to be the male, was killed by a fox.
The question raised was how would the cygnets fare, and would the female find another mate?
Black swans mate for life and are monogamous, but when one dies, the other quickly finds another mate, usually a young unattached bird.
So long as the cygnets escape the fox, and with one parent as guardian, they should survive well enough.
When they nest alone, the pair-bond remains strong, but when swans form large breeding colonies, as they often do, life can become complicated.
Swans are easy birds to study, and by capturing them and fitting numbered collars — as distinct from leg bands — their daily lives can be closely monitored.
The results of the studies have produced some unexpected results.
Although monogamous, they occasionally mate outside their pair-bond.
DNA analysis shows one in three cygnets have “extra-pair paternity”, that is their father is not the mate of their mother.
This is not at all unusual in birds that live in colonies — in the case of fairy-wrens, extrapair paternity occurs in much higher numbers.
Each autumn, swans moult all of their primary wing feathers and for about a month they are flightless.
To best survive this, large numbers gather on major coastal wetlands including Lake Connewarre.
In Tasmania, a large wetland is called Moulting Lagoon for this reason.
When in flight, swans are supreme, their long whitefeathered wings in striking contrast to th their i bl black k bodies bodies. It is then that their fluting call is best heard.
Wildlife sightings and questions can be sent to ppescott@gmail.com