They are undoubtedly first year White-fronted Terns.
Nothing else looks like this, especially this time of year. Specific
features are:
The extensive, triangular dark cubital bar, extending well back towards the
trailing edge of the wing
The dark centred tertials - these are juvenal feathers and it's far too
early to be seeing juvenal Common Tern in Australia
The white upper edge to the primaries, seen beautifully in Tern2 at rest.
This is caused by the way the white on the inner webs of the primaries
extends out towards the tip around the dark marks. It is never seen like
this in Common Tern.
The overall bulky look
In plumage, a Common Tern never looks like this. A closer approach could be
from Roseate Tern, but Roseate is smaller and more delicate, with a long
tail even as a juvenal, and much more slender body proportions.
These are perfectly normal White-fronteds in their first moult, looking just
like they should at this time of year.
Cheers, Chris.
Chris Corben
www.hoarybat.com
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