Seabird Sunday ID CHALLENGE 11 October 2020 P Plate by Janine Duffy
Who is this striking bandit? Seen at Nightcliff, Darwin NT in September.
Size: big for this sort of bird. Behaviour: flying near shore.
Solution:
Australian Tern or Australian Gull-billed Tern Gelochelidon macrotarsa
Until recently this bird was called Gull-billed Tern Gelochelidon nilotica macrotarsa.
When you see this bird in the flesh you’ll immediately notice how white it is, and how big it is. They are one of the palest of our terns, and though you might think you won’t see it – you will.
Size is very helpful too – they are not as big as a Caspian (which is huge) but they are up there with the big guys: just a little smaller than most Crested Terns & similar to a Lesser Crested Tern.
They have a fabulous chunky bill, that really is noticeable – different to the long thin bill of most terns – and though it’s not really straight-edged like a gull bill, it does have that feel.
The biggest problem in identifying this bird is the other species (formerly subspecies) that also pops up in Australia: the Asian Gull-billed Tern ssp affinis. Luckily we have excellent information from Dr Amanda Lilleyman noting the differences back in 2014, before the two were split: http://ntfieldnaturalists.org.au/site/assets/files/1327/ntn25_03_lilleyman_gull-billed_tern_asian_subspecies_in_darwin.pdf
Asian Gull-billed Tern is much smaller – can be half the size – and a little darker, and this brings it closer to the Whiskered Tern, which also can have that white head and black eye mask.
Whiskered Tern in non breeding also has a bit of a chunky black bill.
But luckily this bird, now called the Australian Tern, is so large and pale that you won’t have that trouble.
You’ll notice that eBird hasn’t recognised this new species yet, and still considers it a Gull-billed Tern. So when you put in an sighting, you have to make sure you have the subspecies turned on, and choose Gelochelidon nilotica macrotarsa or Gull-billed Tern (Australian)
Women Birders Australia 