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argenteus or argentatus? - Taunton, UK (1 Viewer)

jamesevry

Well-known member
p10 looks different to usual, and only has a hint of a broken subterminal band. I don't really know which subsp. of herring this indicates, or if there is another more useful feature?
many thanks,
james
 

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p10 looks different to usual, and only has a hint of a broken subterminal band. I don't really know which subsp. of herring this indicates, or if there is another more useful feature?
many thanks,
james

Interesting wing... I have no experiences with argenteus, but I imagine an argentatus would be obviously darker gray than the argenteus to the right...
 
Typical argentatus indeed has darker grey upperparts than argenteus, but there is some overlap. Particularly Danish and eastern Baltic birds can be quite pale. On a Kodak Grey Scale, argenteus has values from 3 - 5.5, while argentatus (including eastern Baltic birds) ranges from 4.5 - 7 (or, exceptionally, 8). Variation in mantle shade appears to be clinal, ranging from palest in Danish birds to darkest in Arctic regions.
Things are complicated by the fact that breeding birds in the north of the Netherlands, north-western Germany and south-western Denmark appear intermediate between the two subspecies.

P10 does not look all that unusual to me. The size of the white mirror is variable, and so is the amount of subterminal black. For instance, an all-white tip to P10 (i.e. total absence of subterminal black) is found in about 10 to 30% of adult argenteus, depending on which part of their breeding range you are looking at. Olsen & Larsson (2003) give c 20% for argenteus. Coulson et al (1984) examined many argenteus (n = 1,484) from various breeding colonies in Britain, and noted the following percentages: 30.9% in Shetland birds, 20.5-25% on the British east coast, 9.3-10.8% on the British west coast, 13.4% in North Wales, and 1.4% in Lancashire, England. They concluded that Herring Gulls breeding on the west side of Britain show on average more black near the tip of p10.

A better character to look for on P10 is the extent of the pale tongue. Argentatus influence is often evident in a long tongue, covering well over half the length of the inner web. Such a tongue seems to be absent here, though it is better judged on the underside of the wing. Other characters that may indicate at least some influence of argentatus are broad, prominent white tongue-tips on P6-8. Argentatus usually has a large white mirror on P9 (covering both webs), but this is also shown by about 35% of argenteus, so do not look to much into it. Better to combine it with the other characters.

In the Taunton bird, the white mirror is limited to the inner web of P9, and a white tongue-tip on P8 is lacking altogether. It looks like a fine argenteus to me, though with a little less black on P5-6 than average.
 
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