Thursday, 21 November 2013

Large numbers of Whiskered Terns in Gippsland

The Wiskered Tern (Chlidonias hybridus), aka Marsh Tern, is found in Africa, Europe, Asia and Australia. There are three sub species hybridus (Eurasia), delandi (Africa) and javanicus (Australia).
Adult Whiskered Tern in breeding plumage - note full black cap, red bill and legs and the dark grey under parts.
Adult bird - Whiskered Terns have a slight V in tail only visible when the tail is closed.
The name Whiskered Tern is derived from the white band seen here between the black cap and the grey under parts. Not a very obvious whisker in my opinion - I think I prefer the earlier name Marsh Tern.
The Whiskered Tern is widespread across Australia during the non breeding season and a rare vagrant to Tasmania. It breeds erratically according to seasonal conditions, but generally from September to December, in southeastern Australia. 
The Whiskered Tern frequents inland waters. It is not a marine species, however it can sometimes be found in estuaries and wetlands near the coast, such as the Gippsland Lakes, particularly the adjacent wetlands. A gregarious species, these terns feed, roost, travel and nest together, mostly in small flocks, however occasionally large flocks containing a thousand or more birds are encountered. They are certainly a nomadic species however some are thought to be migratory moving from the Top End to Indonesia and Asia and back again.
In East Gippsland, we see small parties of Whiskered Terns over our wetlands from time to time. This year we are seeing more flocks than normal and larger flocks. Conditions in East Gippsland are generally good this spring with plenty of water in our wetlands. Inland Australia is drying out following a run of wet years when many water birds took advantage of the favourable conditions to breed up. So perhaps it is not surprising that we are now seeing larger than normal numbers of Whiskered Terns in suitable near coastal habitats as many species head for the coast when inland Australia dries out.
I discovered a larger than normal flock of Whiskered Terns on Wednesday the 6th of November near Hollands Landing, a very small fishing hamlet on McLennans Straits at the western end of Lake Victoria. Returning from a Gippsland Lakes Important Bird Area (GLIBA) survey in the Sale area I decided to detour in to Hollands Landing to check out the birds there – it is a good location for water and shore birds, including migratory wader species.
From Bengworden Road, a back road between Sale and Bairnsdale, driving along Hollands Landing Road I came across a large number of white birds flying low over the flat sheep and cattle paddocks.  It soon became obvious they were Whiskered Terns, well over a 1,000 birds, and they were coursing low over the paddocks. From time to time birds would dive into the long grass. They were clearly feeding. For me this was odd as I had always seen them feeding over water in the past. Like all terns their diet consists mainly of small fish taken by diving into water. Checking some field guides and other reference books later I found that feeding over dry land was not mentioned so I assume this behavior is at least a little unusual.
The bird in the lower foreground has just caught an insect on the ground - see next shot.
Note the small food item in this bird's bill.
In this shot a bird's wings are just visible above the top of the long grass.
It was a marvelous spectacle to stand by the side of the road and watch such a large number of birds in action. In every direction I looked I could see terns over the adjacent paddocks. As they coursed around and back and forth over the paddocks, they alternated between dispersal to chase food and aggregating into strung out flocks. They seemed to randomly follow a leader for a short while and then the flocks would break up again and birds would spread out over a paddock and look for insects in the head down position typical of all terns.
A small section of the leading end of one of many groups in the area. The birds wheeled around and coursed back and forth before breaking up and dispersing over a paddock to hunt. At some undisclosed signal they would gather again to repeat the cycle. They are hard to count however there are nearly 90 birds in this shot alone with another 200 or 300 birds out of the image behind them. And this was only one of many similar sized groups in the area.
As I watched them and took the opportunity to take some photos now and again as random chance brought some of them close enough for photos, the landowner, out checking his stock on a motor bike, came over for a chat. He was interested to know what species of bird they were, as he had not seen them before. He said they had turned up two days earlier (the 4th).
The birds were still feeding over the same paddocks 14 days latter on the 18th of November when a group from Birdlife East Gippsland visited Hollands Landing as a regular Monday outing and to conduct three GLIBA surveys there. The farmer mentioned above has had a valuable service performed by these birds as a thousand birds or more must have converted a lot of pasture eating insects into fertiliser over the 14 days.
Many of the birds were in breeding plumage with black caps, red bills and feet and dark grey under parts. When in non-breeding condition the under parts are white, the forehead white and the bill and feet are blackish.
I wonder if these birds have recently bred or are going to breed? Perhaps the latter as there did not look to be any juvenile birds in the flock – it is not that easy to pick as adult birds in non-breeding plumage look similar to juveniles?
An adult in non-breeding plumage.
Another view of a non-breeding bird - note there is no black cap, just some blotchy patches of black feathers. And the under parts are mostly white though a little blotchy.

1 comment:

  1. How wonderful to see such a large flock. They are "regulars" at Werribee at this time of the year and great to watch as they catch items over and in the ponds.