Slaty-backed Gull (schistisagus) / オオセグロカモメ / 큰재갈매기

(last update: December 2015)

hybrid Glaucous-winged x Western Gull (glaucescens x occidentalis) 1st cycle (2CY), October 28 2011, Elwha River Mouth, Clallam Co. - Washington, USA. Picture: Steve Mlodinow.

Please visit Steve's Flickr photostream, for many more images. And also Dave Appleton's blog on hybrids!

There is an extensive overlap between the ranges of Western Gull and Glaucous-winged Gull and in that overlap zone (between southern British Columbia and southern Oregon) the two species readily hybridise.  Hybrids (known as Olympic Gulls) are not only fertile but in the centre of the zone they have superior fitness over pure birds.  Consequently there is a hybrid swarm of birds showing the full specturm of appearance between the two pure species. 

Note the dark mask of a Western Gull and the rather dark plumage overall with more Glaucous-winged Gull like primaries (but with primary tips still too dark for that species).