fact is hybridization in GBBG is rare. This is the exception in GBBG and
not the rule. Agreed there are a few apparent hybrid GBBG, with GBBG X
Herrring Gull and GBBG x Glaucous Gulls seen very rarely . Any other
possible combos relevant to this discussion ? For the sake of discussion,
I'll say these hybrid GBBGs are less than 1:1000 to pure GBBG.
So is there any pattern of vagrant GBBG being hybrids more likely than pure
GBBGs ? I haven't heard of this. And comparing the likelihood of a Western
Gull hybrid vagrant to Colorado more likely than a pure Western Gull may or
may not be true, but it is a fallacious argument relevant to the GBBG in
Renton because Western Gull X Glaucous-Winged Gulls occur in the hundreds
of thousands and GBBG hybrids are rare.
So lets not call this a possible Herring Gull x Great- Black-Backed Gull.
At the least, it is the first record for Washington of GBBG(hybrid) to
the west coast, and at best it is the real thing. We are talking about
purity here, and that will never be fully agreed upon.
Some photos of the exact colour of these new mantle feathers could be
useful here.
Mike Tabak Vancouver B.C.
( with acknowledgement of your expertise and dedication Phil)