Thursday, 5 June 2014

American Herring Gull x Glaucous-winged Gull

American Herring Gull x Glaucous-winged Gull hybrid, Mukilteo (Washington, USA), January 2011 - copyright Steve Mlodinow
(photo ID: 1470)


This hybrid seems to occur rather frequently in North America - Steve says it's fairly common during winter on the Washington Coast and in the Puget Trough.  To kick off with here's a bird that Steve's managed to capture well both on the deck and in flight.

American Herring Gull x Glaucous-winged Gull hybrid (same bird as in photo ID 1470 above), Mukilteo (Washington, USA), January 2011 - copyright Steve Mlodinow
(photo ID: 1469)


Next up are two first-cycle birds which look quite similar to Thayer's Gull, as seems often to be the way with this hybrid. Steve points out that these birds are already in first-winter plumage in October, whereas Thayer's would not moult into this plumage until mid-winter. He also notes that they have bills that would be rather hefty for a Thayer's Gull.



American Herring Gull x Glaucous-winged Gull hybrids, Hobuck Beach, Clallam County (Washington, USA), 27th October 2013 - copyright Steve Mlodinow
(photo IDs: 1125-1126)


Next is another that could easily be mistaken for a Thayer's Gull.  Steve notes the short primaries and bit of a secondary "skirt" (secondaries visible below folded wing coverts).  He points out that the secondary skirt is mostly a feature of large west coast gulls such as Glaucous-winged Gull, Western Gull, and Slaty-backed Gull.  He also notes that the greater wing coverts are not evenly speckled, as they should be in a juvenile Thayer's Gull, and that the bird is moulting in first-winter (grey) feathers among its scapulars, something which Thayer's Gulls rarely do before January.  The brownish primaries, secondary skirt and shortish primaries also argue against Herring Gull.  Steve adds that the bird's large-chested and small-headed look are typical of Slaty-backed Gull, but this bird lacked that species' white rump and the first winter grey feathers are not dark enough.


American Herring Gull x Glaucous-winged Gull hybrid, Larimer County Landfill (Colorado, USA), 1st December 2014 - copyright Steve Mlodinow
(photo IDs: 1690-1691)


Here's Steve's commentary on the next bird, taken on the same date and at the same place as the last:
"I was uncertain about this bird's identity and so sought other's opinions.  I feel that the primaries are a bit too dark for "pure" Glaucous-winged Gull (if such a beast exists), but others disagree.  The chesty and big-billed look are wrong for Thayer's Gull.  However, the extensive mottling at the base of the outer tail feathers seems outside the range of Glaucous-winged Gull, and so points back to Glaucous-winged Gull x Herring."




presumed American Herring Gull x Glaucous-winged Gull hybrid, Larimer County Landfill (Colorado, USA), 1st December 2014 - copyright Steve Mlodinow
(photo IDs: 1707-1711)


This bird stuck around and here Steve describes his next encounter:
"It is a frankly peculiar bird.  Perched, it looks more like a Thayer's Gull, due to smallish looking head and bill, though the body seem rather fat for its head, imparting a Slaty-backed Gull like shape (though the plumage is utterly wrong for that species).  In flight, the bird looks bigger, even larger billed. I took stock by asking for opinions from Washington and Alaska, and they agreed with the Glaucous-winged x Herring diagnosis, though certainty must be elusive."


presumed American Herring Gull x Glaucous-winged Gull hybrid, Larimer County Landfill (Colorado, USA), 16th December 2014 - copyright Steve Mlodinow
(photo IDs: 1714-1716)


Here's a thayeri-like adult from the same visit.  Steve says:
"At first glance, this bird recalls a hefty male Thayer's Gull.  However, it was at least as big as the larger Herring Gulls about.  The barred smudging on the chest resembles that of a Glaucous-winged Gull.  The wing extension past tail is on the short side for Thayer's Gull... and the white spotting on the wing would be rather reduced for Thayer's Gull as well."

American Herring Gull x Glaucous-winged Gull hybrid, Larimer County Landfill (Colorado, USA), 16th December 2014 - copyright Steve Mlodinow
(photo IDs: 1714-1716)


Steve's next one a few days later looks a little different:
"Note the huge bill, medium brown wingtips and secondary skirt.  Indeed, this bird (perched view) could be taken for a Glaucous-winged x Western Gull, but the spread wing views show rather pale wings and barring at base of outer tail feathers, a Herring Gull character."



presumed American Herring Gull x Glaucous-winged Gull hybrid, Larimer County Landfill (Colorado, USA), 22nd December 2014 - copyright Steve Mlodinow
(photo IDs: 1719-1722)


And a second bird, same place, same day:


presumed American Herring Gull x Glaucous-winged Gull hybrid, Larimer County Landfill (Colorado, USA), 22nd December 2014 - copyright Steve Mlodinow
(photo IDs: 1717-1718)


And a third, this one an adult (as was a fourth).  Steve tells us that one more like Herring Gull but this one was closer to Glaucous-winged Gull.  The folder primaries are a little too dark and the eye was pale.  Some apparent Glaucous-winged Gulls do have pale eyes but it's a rare feature in that species.



American Herring Gull x Glaucous-winged Gull hybrid, Larimer County Landfill (Colorado, USA), 22nd December 2014 - copyright Steve Mlodinow
(photo IDs: 1723-1725)


Steve separates the next one from Thayer's Gull by its heavy bill and Glaucous-winged Gull like smudging on chest.

American Herring Gull x Glaucous-winged Gull hybrid, Hobuck Beach, Clallam County (Washington, USA), 27th October 2013 - copyright Steve Mlodinow
(photo ID: 1144)


For the next one Steve writes,
"The intermediate primary darkness (between Herring and Glaucous-winged Gull) points to either Thayer's or Glaucous-winged x Herring Gull.  However, the muddy plumage in a first cycle bird (not the crisp speckled plumage of a juv/1st winter Thayer's in January) eliminates Thayer's Gull as does the relatively short primary projection.  Note the odd bill from digging in the mud after rotting fish carcasses.  Yummy!"
For the flight photos he draws attention to the bird's size, the intermediate primary darkness and that a first-cycle Thayer's Gull at this time of year should have less grey on the back as well as more speckling on the greater coverts.



American Herring Gull x Glaucous-winged Gull hybrid, N Teller Lake, Boulder County (Colorado, USA), 20th January 2013 - copyright Steve Mlodinow
(photo IDs: 1221-1223)



American Herring Gull x Glaucous-winged Gull hybrid, Elwha River Mouth, Clallam County (Washington, USA), 28th October 2011 - copyright Steve Mlodinow
(photo IDs: 1365-1366)


For the next bird Steve writes,
"In this photo, the bird has a very Thayer's Gull like aspect.  It is, however, rather short winged and molt is more advanced than that species would normally show in April.  The bird's bill looks delicate for a Glaucous-winged Gull and the primaries a bit on the dark side for that species."
 
American Herring Gull x Glaucous-winged Gull hybrid, Drake Lake, Weld County (Colorado, USA), April 2011 - copyright Steve Mlodinow
(photo ID: 1402)


In these flight shots Steve points out that the white underwing (like Glaucous-winged or Thayer's Gull) is apparent but the bird's bulk is far more like Glaucous-winged Gull. There is also too much dark on the upper primaries for pure Glaucous-winged Gull, and the bill looks petite for Glaucous-winged Gull.




American Herring Gull x Glaucous-winged Gull hybrid, Drake Lake, Weld County (Colorado, USA), April 2011 - copyright Steve Mlodinow
(photo IDs: 1403-1406)


On the next bird Steve says the wings are too short for Thayer's Gull and the dark on the primaries is too extensive.


American Herring Gull x Glaucous-winged Gull hybrid, Brumfield (Colorado, USA), 21st February 2010 - copyright Steve Mlodinow
(photo IDs: 2196-2197)


About the next bird Steve says,
"In some ways, this bird superficially resembles a Herring Gull, with its pale eye and blackish wingtips... but the eye is pale, not the usual white/near-white of a Herring Gull, the bird is rather stout, and the wingtips were not quite as black as they seem in these photos."

American Herring Gull x Glaucous-winged Gull hybrid, Long Beach Peninsular, Pacific County (Washington, USA), 23rd October 2015 - copyright Steve Mlodinow
(photo IDs: 2299-2300)




American Herring Gull x Glaucous-winged Gull hybrid, Everett (Washington, USA), 12th April 2009 - copyright Steve Mlodinow
(photo IDs: 2225-2227)


American Herring Gull x Glaucous-winged Gull hybrid, Sequim, Clallam County (Washington, USA), February 2009 - copyright Steve Mlodinow
(photo ID: 1533)


American Herring Gull x Glaucous-winged Gull hybrid, Chehalis, Lewis County (Washington, USA), December 2009 - copyright Steve Mlodinow
(photo ID: 2224)


Lastly a bird I saw on holiday in British Columbia.  I didn't identify it correctly at the time but it has been pointed out to me that it is most likely an American Herring Gull x Glaucous-winged Gull hybrid, albeit with a caveat that other hybrids may not be ruled out.  It strikes me as being much more boldly patterned compared to Steve's birds above - perhaps that's just because it's earlier in the season, but as always, comments are welcome.

probable American Herring Gull x Glaucous-winged Gull hybrid, Esquimalt Lagoon (Vancouver Island, British Columbia), 9th September 2006 - copyright Dave Appleton
(photo ID: 0537)


American Herring Gull Larus (argentatus) smithsonianus
Glaucous-winged Gull Larus glaucescens

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