12,000 unidentified gulls sounds appropriate to me! Unless a bird fits a particular species profile pretty well, I think it should be left unidentified. I have followed these discussions, first on the ID-Frontiers listserv and in recent years on the various Facebook groups, and grappled with the West Coast hybrid issues when I lived in California. I’m a molecular biologist and geneticist, as well as a birder, and I cringe at the confidence by which some identify the various hybrids. I have two main problems with this:
We don’t really have enough information on what the various hybrid combinations look like at various ages. To get this data would require either (i) color-banding offspring in nests of mixed breeding pairs and then following the development of the hybrid offspring’s plumage, or (ii) genotyping suspected hybrids so that plumage characteristics can be associated with known hybrid genotype. For the most part, this just hasn’t been done. For hybrids like Western x Glaucous-winged on the U.S. West Coast, these are so common (indeed, often outnumbering “pure” examples of the parent species) that assigning birds with mixed characteristics as “Olympic” Gulls has a high probably of being correct. But for the less frequently encountered hybrid combinations (Cook Inlet, Seward, Appledore etc), or birds out of range, how confident can we actually be in reality? Without hard empirical data on what the plumages of birds with known hybrid genotypes actually look like at various ages, not very. Not a popular opinion, I know, but I think that’s the cold hard reality
The other problem I have with identifying hybrids is, what does it actually mean to identify a particular individual as a “hybrid”? Do we mean it’s an F1 hybrid produced by the pairing of “pure” parents? Is it an F2? Is it a backcross between an F1 and a “pure” parent of one of the original species? F1 x F2? Again, we have no idea! It’s potentially a genetic mess out there. And there simply isn’t the data available, matching phenotype with hybrid genotype, for us to know. We’ve set up these designations for the various hybrids - “Olympic”, “Seward”, “Cook Inlet”, “Viking” - sounds good, but what do we actually mean? F1? Or are these just a grab bag for anything that looks intermediate (it should be the latter, if we use them at all). Giving them names is cute, but for me it sort of implies that these beasts are something better defined than they really are.
I know this is unpopular because it’s ingrained to put a name to everything we see and leave no bird unidentified, but if we want to maintain the scientific integrity of gull identification, I really think the vast majority of these gulls SHOULD be let unidentified, or the identification should be left as PUTATIVE species A x species B, at best, until we have better information.
Sorry if that sounded a bit rant-y!