To me it makes no more sense to dismiss hybridization amongst those two species as a mechanism for primary darkening than it does to invoke it. Just because it's not proven doesn't mean the alternative is true either. It would be one thing if, say, glaucoides in Iceland (the country) were darkening its primaries or Glaucous Gulls or even (American) Herring Gulls were seen to do so, but I'm not aware of any such trend. A Western birder might find the idea that two similar gull species *not* hybridizing to be alien to their experience, for example.
>From my POV it makes sense to attempt to normalize intra-(sub)species variation by looking at that spread in Iceland glaucoides populations in, say, Iceland itself. While more or less anything can happen with gulls, I'd be a lot less likely to find the "intrinsic variation" idea worthy of Occam's Razor if the range of variation in the bird-oft-referred-to-as-Kumlein's substantially exceeds that in the glaucoides subspecies. Or, more plainly put - point me to the preponderance of evidence that hybridization is *not* going on in this form of Iceland Gull (or whatever it is). Phil On Thu, Jan 16, 2014 at 12:29 PM, julian hough <jrhou...@snet.net> wrote: > Shai distilled down some common-sensical aspect of the complications > surrounding Iceland Gulls and what our perceptions are about how solid > these are as a taxon. As an exiled Brit, I grew up on nominate > glaucoidesIceland Gull and it often involved searching through these for a > vagrant > kumlieni "Kumlien's" Iceland Gull. > It is more a continuing bad-habit that I refer to them as Kumlien's Gull > here since, as Shai points out, there really isn't that much of a need for > separating them to sub-species level in the US, as perhaps there is in > Europe where kumlieni shows up more regularly. > > Interestingly, adult iceland Gulls were scarce here in New England > compared to the numbers of first-cycle birds so it was always cool to see > an adult. The ones I have seen here in CT have all been mid-grey – to pale > grey pigmented and black-primaried individuals seem rather uncommon at this > latitude. Not sure that as quantitative evidence it amounts to anything > from a scientific aspect but I wonder what drives the range of pigmentation > in these birds…hormones, geography, actual hybridization? > > There seems to be a lot of talk – confusion – is perhaps more apt about > what these birds are based on perpetuated myths about "hybrid swarms "of > kumlieni or interbreeding populations of kumlieni x thayeri etc and as > Shai points out it may not benefit us, in lieu of quantitative and > qualitative scientific study, to continue thinking that black-primaries > Iceland Gulls here in the US have "x" amounts of thayeri genes flowing > through them and more whiter-primaried birds have perhaps a more > glaucoides influence. > > As for separating adults from nominate glaucoides Iceland Gulls from > Northern Europe, certain birds in Newfoundland seem to check the right > boxes so with care the odd bird might be identifiable by sharp observers. > > Intrestingly, the long-calls of these white-winged gulls was recently > studied and written up by Belgium birder Peter Adriaens here: > > http://birdingfrontiers.com/2014/01/09/calls-of-thayers-kumliens-and-iceland-gulls > / > > Good birding, > > Julian > > Julian Hough > New Haven, CT 06519 > www.naturescapeimages.wordpress.com > > > -- > *NYSbirds-L List Info:* > Welcome and Basics <http://www.northeastbirding.com/NYSbirdsWELCOME> > Rules and Information <http://www.northeastbirding.com/NYSbirdsRULES> > Subscribe, Configuration and > Leave<http://www.northeastbirding.com/NYSbirdsSubscribeConfigurationLeave.htm> > *Archives:* > The Mail > Archive<http://www.mail-archive.com/nysbirds-l@cornell.edu/maillist.html> > Surfbirds <http://www.surfbirds.com/birdingmail/Group/NYSBirds-L> > BirdingOnThe.Net <http://birdingonthe.net/mailinglists/NYSB.html> > *Please submit your observations to **eBird*<http://ebird.org/content/ebird/> > *!* > -- > -- "If you lie to the compiler, it will get its revenge" - Henry Spencer -- NYSbirds-L List Info: http://www.NortheastBirding.com/NYSbirdsWELCOME http://www.NortheastBirding.com/NYSbirdsRULES http://www.NortheastBirding.com/NYSbirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/nysbirds-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/NYSBirds-L 3) http://birdingonthe.net/mailinglists/NYSB.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
