Tern, tern …

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.

tern8

Whiskered Tern (adult in breeding plumage), Cairn Curran, 3rd February 2017

whiskered1

II

whiskered2

III

tern2

White-winged Black Tern (immature) – white rump and black ear coverts

tern4

White-winged Black Tern

tern1

Not sure on this one …

tern7

White-winged Black Tern – juvenile/immature?

tern5

White-winged Black Tern

tern3

White-winged Black Tern

tern6

White-winged Black Tern

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.

6 responses to “Tern, tern …

  1. Carol Summerhayes

    Geoff – great photos which I sent on to a tern expert friend – she wonders if we are looking at juvenile whiskered terns but is away from her bird books and would like to consult them before opining! Shall let you know.

  2. Carol Summerhayes

    Sorry – typo in earlier email address

  3. Hi Geoff. I looked at HANZAB and it appears that all the immature birds are probably Whiskered Terns. I’d have to to some serious research to check the timing of moults but it stands to reason birds in such juvenile plumage would have to have been locally bred (very likely with such good habitat this season).

    • Hi George – thanks for the note. I’ve looked at HANZAB also and tend to agree with you. What still puzzles me is the size difference between the juveniles and adults – the juveniles had significantly smaller bills and were finer, less bulky. The weight of evidence though seems to suggest they are all Whiskered, esp the mottled plumage.
      All the best, geoff

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