Tweeters,

Regarding Mike Denny's query whether the Lesser Black-backed Gulls (LBBG)
seen in WA could be Heuglin's Gulls. No, we don't know for sure if of the
some of the birds reported as LBBG could possibly be Heuglin's, but it is
extremely unlikely. The pattern of occurrence fits LBBG perfectly. The
increase in records of LBBG was preceded by a clear increase in record of
this species in other western states, particularly Colorado which gets the
best coverage of any western state excluding Pacific coastal states. The
records are mainly from the the eastside if WA, at least suggesting that the
origin of these birds is from the east. While there are a few isolated
records of unknown dark-mantled gulls with yellow legs from Alaska, there
are no solid records of Heuglin's Gull and no pattern of occurrence. If the
record of the the LBBG-like gulls were actually Heuglin's it would seem
likely that the records of these birds would be more evenly distributed
between the both sides of the Cascades and probably more frequent on the
west side of the state.

Additionally, only nominate Heuglin's Gull is really difficult to separate
from LBBG. This race breeds in extreme western Siberia (right upto the
border of Finland) and moves largely west in fall (toward Europe, away from
Alaska. It's confusing on the other side of the globe!) and then south into
the Persian Gulf region. This makes the likelihood of its occurrence in WA
somewhere between low and pretty darned low! The other races of dark
mantled gulls breeding in northern Siberia, vegae, birulai, and tamyrensis
all should be reasonable easy to separate from graellsii LBBG. So while it
is hard to be absolutely certain that everything reported as LBBG is a true
graellsii LBBG, I would be willing to bet most of my fingers and all of my
toes that they all are.


Cameron Cox

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