Unknown bird, Darwin Harbour

["Mike Carter" <>]

I emailed Bill Stent to tell him I reckon that his bird is either a 
Whiskered or a White-winged Black Tern. At first glance the dark eye blotch 
seems to suggest Gull-billed Tern but it is wrongly inclined. That mark on 
Gull-billed Tern slopes down from forward of the eye, such that the rear of 
it is more distant from the crown than the forward edge. On Bill's bird it 
slopes up as would head markings on non-breeding Whiskered or White-winged 
Black Tern. Also, as Peter notes, the outer tail feathers are not long 
enough to create a fork when closed. Both the above features are visible in 
the photo to which Russell drew our attention. I also agree that the legs 
really are red, matching both of the marsh terns, contrary Gull-billed which 
are black. What gives the head markings the reddish tinge, must however be 
aberration.
Mike Carter
30 Canadian Bay Road
Mount Eliza  VIC 3930
Tel  (03) 9787 7136