A comment (thanks Rob) on my recent post regarding Whiskered Terns has been most welcome.
First, some context – Whiskered Terns Chlidonias hybrida are similar to another species, the White-winged Black Tern Chlidonias leucopterus, which is rarely seen in inland Victoria. The latter is a summer migrant which breeds in Northern Europe and Asia and visits coastal areas in Australia from October to April each year. They are much more common in western and northern parts of the continent but regularly recorded in Port Phillip Bay, the Western Districts and the mid-Murray Valley, all places where wetlands are more reliably wet.
The key differences between the two species (in non-breeding plumage) are that the White-winged Black Tern:
- is smaller and has a more buoyant, fluttering flight
- has a shorter tail and an all white rump, compared with a grey rump on C. hybrida
- has smutty-black ear coverts (that look like headphones!)
- has pinkish legs while the legs of C. hybrida tend to be a dark-red or black
The birds photographed below were part of a small, loose flock fishing in the Joyce’s Creek section of Cairn Curran. The adult Whiskered Terns are easily distinguished with their bright-red bill, black cap and sooty underparts. White-winged Terns in breeding plumage are black all over with contrasting grey wings and white shoulders but its unusual to see them in this garb in Australia. Non-breeding and immature individuals were much more difficult to separate although I’m fairly confident with the identification attached to the images below. Seen together, the size differences were evident, as were their calls. As will be clear from this note I’m not well acquainted with the White-winged Black Tern, so would be very happy to receive any additional thoughts on the birds in this post and that from earlier in the week.
Correction: These terns have been the subject to a fair bit of examination and conjecture over the past week and the feeling now is that they might all be Whiskered Terns, with the supposed White-winged Black Terns, recently fledged juveniles of the former species. I’ve left the text above for now to show my original reasoning.