Thanks to all who have commented on my questions about hybrid "Olympic
gulls". I'll try to find some time to go to the library and look for the
references cited.

I take no position on whether these birds should be called Olympic, Puget
Sound or Gw x W, but wegugwgu is horrendus.

However, I am still confused about the hybrid vs. subspecies issue. Given
that species are inventions of the human mind that may not correspond
exactly to real biology, and given the long history of controversy over
the definition, it nevertheless seems true that most definitions start
somewhere near the idea of a gene pool of fertilely interbreeding organisms
reproductively isolated (under normal circumstances) from other organisms.

When a fertile "hybrid" occurs as commonly under natural circumstances as
the wegugwgu does, it is hard to argue for even minimal reproductive
isolation of the parental "species". The NatGeo guide book suggests that
even western Gulls "proper" show a south to north cline of coloration
which seems to be extended by the "hybrids" up to the glaucus-winged.
Based on my limited knowledge of the facts, it seems to me that it would
be more natural to treat these as subspecies or geographical varieties.

Are GW and W gulls considered separate species because historically these
two forms were identified by ornithologists before the intermediates
were? Or is there some evidence that in evolution they separated
(geographically?) into two non-interbreeding forms only to later meet and
resume interbreeding?

I was intrigued by the suggestion that they could be considered separate
species if at least 5% of gulls in the "hybrid zone" were parentals. My
own inclination would be to consider the "parentals" conspecific if there
were more than about 25% fertile hybrids, since most "good" species would
show far fewer than 5% fertile hybrids. There are certainly exceptions
(several Hawaiian examples come to mind), which is why the definiton of
species remains controversial.

Paul Talbert
Pacific Lutheran University
Department of Biology
paul at sparky.fhcrc.org