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Just got sent this by Adam C from the Ashley Rakahuri estuary this evening. A nice Arctic tern going into Breeding plumage. Straight out from Kings Ave amongst the WFT and BFT flock.

Also present was the red-billed common tern that’s been present in recent times.

Here are the pics and the Red- Billed Common that was present too.

top bird looks more like the Antarctic tern that has been hanging around as a arctic would still have a lot more black on its bill until it has moulted into breeding. The bottom bird looks more arctic to me than common tern and it also fit breeding cycle as a arctic would be moulting into breeding plumage around now.

Hi Tim. Canterbury birders have been following the 2 common terns most of the summer at the Ashley and they have been identified as such by other birders. It's the first time I've caught up with the red billed one ( much more advanced towards breeding now) but I've been getting to know the darker billed one and you can pick them by stance and attitude alone in the field. This one you could pick from quite a way back. Question is is it Longipennis or classic hirundo? Re Arctic I think Antarctic would have a dark red bill now and those short little legs seem classic Arctic but I couldn't say 100% but other birders have called Arctic on this one but certainly open for discussion! Agree it's an odd mix of bright red bill and cap yet to catch up?

heres some links from most likely the same Antarctic tern.
viewtopic.php?t=12490
viewtopic.php?f=9&t=12638&hilit=antarctic

still leaning towards arctic for the bottom bird as I have seen long legged arctics before and it jusr depends on there pose.

Here's the bird on 4th of March.

Here’s the bird on the 16th of March and 1st of April. Coming into breeding plumage nicely.

Hopefully the below clears all this up with photos and comparisions.
For the first bird checking this on a desktop it is very clear that it is not an Artic tern but the exact same Antarctic Tern that was photographed at the Mole and the one around lake Ellesmere.
You can see if you look closely at the bill all the photos show the same black dirty mark at the top of the bill near the face but there is some variation in the head moulting as photos were taken at different times, it even has the same white feather mark on the middle shoulder as the Ellesmere bird indicating that it is the same bird.
See photos below


For the other bird its I am pretty sure it is an Artic tern that is entering breeding plumage, both photos where shot in different lighting conditions so there are factors that one looks a lot more grey than the other, I expect the Ahsley bird to get a lot more of the blood red colour on the legs and bill as it moves closer to breeding plumage.

For the non breeding photos you can see that it compares quite well to the Artic tern that I found back in Hawkes Bay, that bird had the same leg structure as the Ashley bird, the difference in the photos was lighting where the bird I photographed looked more silver but when the light got brighter it was same grey as Ashley bird, it also had bits of red showing at the base of the bill.


If you think that the bill is too large and doesn't suite an Artic tern remember the South American Tern that was then changed to an Artic tern with large bill by the records committee as they said there could be some variation in bill length and that bill is large for an Artic tern.


I remember there was more Artic terns being reported 5-10 years ago and now they have dropped off and more common's being reported, it could be possible that many of the common's being reported are Artic terns in 1st year plumage.

The bird with red bill and red legs looks as if it is still growing the outer (P10) primary - feather score 4.

Great discussion.
If this is the case then we have all 3 birds here.
Common, Arctic and Antarctic but I still think the legs on the middle bird are way too long for Arctic but it's difficult to be sure!