Argentatus vs michahellis, 02.10.07
To find and identify correctly an adult Herring Gull amongst a flock of YLG in Switzerland at this period of the year is often very difficult. Many pictures labelled "Herring" taken in september or october in Switzerland show often 3 o 4 cy YLG with a relatively heavy streaked head and still fleshy legs (often accentuated with particular light) or an adult YLG like that one (1).
Except the classical ID criteria, the timing of the primary moult seems very useful. The bird I found at the end of September is interesting (compare the two flight shots below). Argentatus : inner primaries are new, P8 starts to grow and P9-10 are old / Michahellis : all primaries are new except P9 and 10 that grow.
Other pics of this ad Herring (2, 3)
Because of the primary moult YLG gives also the strange impression to be shorter-winged that Herring (4)
This matter is not new for gullers but could be interesting to keep in mind for other birders (particularly in my country where Herring Gulls are rare).
Complete galleries (and pics with bigger size) of Herring Gull here and YLG here.
Except the classical ID criteria, the timing of the primary moult seems very useful. The bird I found at the end of September is interesting (compare the two flight shots below). Argentatus : inner primaries are new, P8 starts to grow and P9-10 are old / Michahellis : all primaries are new except P9 and 10 that grow.
Other pics of this ad Herring (2, 3)
Because of the primary moult YLG gives also the strange impression to be shorter-winged that Herring (4)
This matter is not new for gullers but could be interesting to keep in mind for other birders (particularly in my country where Herring Gulls are rare).
Complete galleries (and pics with bigger size) of Herring Gull here and YLG here.
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