Re: The Not-A-Glaucous Gull (possible Kumlien's - pictures)
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Alvaro, Jerry, and everyone else interested in this mind-numbing gull debate:
I agree that kumlieni is genetically intermediate between thayeri and glaucoides. BUT I don't think that makes it not be a valid taxon. Looking at the range maps in Howell & Dunn's book, I can see only a tiny area of contact between kumlieni and thayeri, none between kumlieni and glaucoides, and none between glaucoides and thayeri. So, if kumlieni is in fact a hybrid populiation, it would have to have arisen sometime in the past, at a time when the ranges of glaucoides and thayeri overlapped. At this point in time, glaucoides and thayeri don't overlap, and kumlieni is a more or less isolated intermediate population. The big question is: When does such a population stop being a hybrid swarm and start being a taxon?
As an example of hybrid speciation, the recently described Appalachian Tiger Swallowtail -- an eastern relative of our Western Tiger Swallowtail (the big yellow city swallowtail) -- is considered a hybrid species that arose from contact between Eastern and Canadian Tigers. So if this kind of thing happens with butterflies, why not with gulls? Kumlieni has little or no range overlap with its relatives, and is more or less phenotypically distinct (a lot more gray-winged birds than white or black within its range), so why isn't it a hybrid species (or subspecies)?
The situation with Western and Glaucous-winged seems very different, in my opinion. There is no place where only hybrids breed. Even within the "blend zone", a hybrid may mate with another hybrid or a pure bird of either species. That is what I would call a bona fide hybrid swarm. But if a hybrid population is isolated so that hybrid birds only breed with each other -- never with pure birds of either species -- as is the case with kumlieni -- might that population qualify as a valid taxon?
Just my thoughts on this very complex issue...
On Wednesday, January 8, 2014 1:12 PM, Alvaro Jaramillo wrote:
There is no way to know, you have to decide in the same way you decide that a bird is a Western and not a Western x Glaucous-winged hybrid. It is a question of degree, as based on all available evidence Kumlien’s is a population of mixed genes (Thayer’s x glaucoides).
This is what I wrote to Stephanie:
It is all about definitions. The way I view it, based on the work of various biologist, mainly Canadians. There is a large hybrid swarm in the northern and eastern Arctic between Thayer’s in the north/west and glaucoides Iceland in the south/east. These birds are Kumlien’s, I do not think that kumlieni is a taxon, but a hybrid swarm. Therefore there is nothing such as kumlien’s x Thayer’s as that would also be a kumlien’s. Now my view does not conform to the current taxonomy of the AOU, so I have to bend a little in trying to identify a bird, as sometimes we are identifying things that are really not well defined (Kumlien’s). One thing that has never been defined, and has never been talked about seriously by scientists is the concept of Kumlien’s x Thayer’s, the assumption is that these are Kumlien’s, so you either accept as a Kumlien’s or as Thayer’s, there is nothing in the middle… that is Kumlien’s.
From: EBB_Sightings@... [mailto:EBB_Sightings@...] On Behalf Of Noah Arthur
Sent: Wednesday, January 08, 2014 1:05 PM
Subject: Re: Fwd: [EBB_Sightings] RE: The Not-A-Glaucous Gull (possible Kumlien's - pictures)
Thanks everyone for your continued interest in this bird! Jerry, thanks for refinding the bird and taking such great photos!
Stephanie, could you forward this email to Alvaro? I don't think I have his email address.
I agree the bill is big for Kumlien's, but not out of the range of variation (if you look at pictures from the East, you'll see some really big-billed ones, even some with strong gonydeal angles, but with plumage much too pale for Thayer's).
And I agree that it's possible that some Thayer's could have primaries this pale, but my question is: How do we know for sure that such birds aren't Kumlien's Gulls? If Kumlien's Gulls in the east often have primaries this color, and can have a bill as big as this, then how can we be sure that this bird (and others like it) aren't Kumlien's? Is there any proof that such birds are in fact Thayer's?
On Wednesday, January 8, 2014 12:35 PM, Jerry Ting <jtnikon@...> wrote:
Here is the reason why I don't think it's a pure Thayer's:
The dark web on the outer primary should be equally distinct from P6-P10 for the Thayer's which is not the case on this bird.
I do think the bill size is problematic though.
On Wednesday, January 8, 2014 12:13 PM, Jerry Ting <jtnikon@...> wrote: