Friday, 30 December 2011

American Herring Gull/Dark Argentatus?

Four hours gull-watching yesterday at Backworth/Seghill began to produce some interesting individuals. First up is a 1st-winter 'Herring Gull' that bears more than a passing resemblance to 1st-winter American Herring Gull. I watched this individual for some 30+ minutes and made the notes below in the field; all images are once again Iphone-scoped hence the poor quality.
I didn't see this individual in flight nor did I see the underwing so unless it gets re-found and flight views/better images produced putting it in the box of either dark argentatus or smithsonianus with any certainty is difficult but from what I saw I believe it is at least as good a candidate as this though to provide some balance see here and anyone seriously interested in proving/disproving it may find this useful.


Compare the more typical 1st-winter 'Herring Gulls' left and below in the 1st image. Note the bill in the 2nd shot above, the basal half beginning to acquire a pinkish base.



Notes
1st-winter, dark almost uniform 'chocolate' brown, lacking  much tonal contrast between upperparts and underparts. Underparts showed some paleness around lower throat/upper breast but otherwise fairly uniform through to vent. Mantle/Scapulars showing some 1st-winter feathers, dark-centred (black) and fairly plain with little in the way of pale edges. Juvenile coverts dark, again showing little by way of paleness or barring. Greater coverts plainish brown based on outers with paler buff edges; inner greater coverts showed some barring.
Tertials dark centred with fairly narrow pale fringes, towards feather tips, the tertial step was obvious.Primaries black with faint pale tips. Tail-band appeared solidly dark and uppertail coverts were heavily barred as were the undertail coverts. Bill parallel edged without strong gonys angle, developing pink-ish base towards basal half. Legs dark pink

6 comments:

Andrew Kinghorn said...

As a layman I would say this was an extremely good candidate for American Herring Gull. This bird is surely worth being put out as a possible Alan?

alan tilmouth said...

There has never been an 'East Coast' AHG so the balance of probability errs towards argentatus... until someone gets better images ;)

Andrew Kinghorn said...

It's almost as absurd as a Glaucous-winged Gull...oh...er ;)

Stewart said...

Looks a bit too mottled on the breast for me Alan. The images of distinctive 'smickers' ( do you like it, I have all the jargon) have a more bonxie /south polar coloured, quite plain underparts, lacking that vermiculation. Saying that, I bet in the states you get HGs that look just like some agrgentatus too...

Unless you can get frame filling shots of it on the deck and in flight, its best to leave it as 'H gull race /sp'. As we have discussed before, not all birds can be assigned to a race. If they could, especially with large gulls, their taxonomy would be a doddle!

alan tilmouth said...

Certainly the classic (easier to identify) smiths are either early juveniles with the 'velvet' underparts or later into 1st-winter with the more obvious bill pattern combined with other features.

I'm not going to get frame fillers of this, large flock/centre of the field = unapproachable, but maybe someone with better digi kit might.

As it stands it wouldn't get accepted by my mother let alone a Rarities Committee and I understand not only the balance of probability as well as the difficulty of establishing any certainty here but as Andrew astutely pointed out if somebody had assigned the GWG last year to just a 'funny looking Herring Gull'.....

Anyway I have to have some justification for spending hours at the tip :0

Stewart said...

Far better just take your Christmas wrappings and forget the gulls ;)

As for the Glaucous winged being a funny Herring gull, was that my mothers record :))