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argentatus/argenteus p10 (1 Viewer)

Paul Brooks

Well-known member
Just watching an adult Herring Gull here in Northumberland UK and I have a question about wing-tip patterns. How much of a feature is the lack of a p10 sub-terminal band for argentatus? The bird I'm watching has no sub-terminal band on p10, giving it a large white tip rather than a p10 mirror. it has a mirror plus white tip on p9.

Am I reading too much into this as a feature or is the large white tip but no mirror an important argentatus feature?

Cheers.
 
always in combination with other features, paul: tatus is bulkier, darker (mantle) and usually has less black in wing tip. don't know how often argenteus with all white p10 tip occure, but i'm sure they exist. i don't live in teus-land, maybe peter (adriaens) or steve arlow can help with this specific trait.
 
I'm sure that you are correct that argenteus do occur without a p10 sub-terminal band. I'm really not sure in what proportion though so I thought I'd put it out there. If anyone has an insight I'd be grateful.
 
There are plenty of birds in Aberdeen at this time of year without sub terminal bands on p10. I think I read somewhere that older males were more likely to show this feature - but don't quote me on that!
 
There are plenty of birds in Aberdeen at this time of year without sub terminal bands on p10

Hi, do you mean you have plenty of argenteus without the p10 sub-terminal band or that your argentatus' exhibit this also?

All else being equal I'd have had today's bird as an argenteus (structure and greyscale) so I'm sure that's what it is, but it did get me wondering about geeking out more on primary tips for a while.
 
There are plenty of birds in Aberdeen at this time of year without sub terminal bands on p10. I think I read somewhere that older males were more likely to show this feature - but don't quote me on that!

it's true that on average males are more likely to show larger mirrors and of course the older the bird the more likely it is to show large mirrors (this is a general rule in large gulls).
 
Hi, do you mean you have plenty of argenteus without the p10 sub-terminal band or that your argentatus' exhibit this also?

All else being equal I'd have had today's bird as an argenteus (structure and greyscale) so I'm sure that's what it is, but it did get me wondering about geeking out more on primary tips for a while.

Well they're breeding in Aberdeen so the assumption is that they're argenteus - and they certainly look like argenteus in mantle tone.
 
Hi Paul,

when I was studying variation in primary pattern of European and American Herring Gulls for the Dutch Birding paper, the complete lack of a subterminal band on P10 was found in 32% of our sample of argenteus (58 birds out of 182). So it is quite normal, and you will probably find many more examples if you keep looking for them among your local birds.

You can read all about primary patterns of Herring Gulls in Adriaens & Mactavish 2004 (online at http://gull-research.org/papers/papers3/DB26_3_2004.pdf).
 
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