Tuesday, February 5, 2013

Herring Gull: that name covers a lot of stuff

A flotilla of Herring Gulls (mostly) floats in Lake Erie near downtown Cleveland. Quite a diverse crew, eh? Someone new to gulling could be excused for thinking them all to be different species.

It takes a Herring Gull about four years to achieve its adult plumage, and every age class floats in the scene above. The dark brown birds are first and second-cycle gulls; they'll become cleaner, neater, and grayer and whiter with age.

A young (second-cycle [I think]) Herring Gull protects its bloody shad by loudly bugling at some interloper.

Leg color can be an important identification characteristic; generally speaking, Herring Gulls have pink legs. I believe this is a first-cycle bird, with neatly patterned wing coverts and mostly dark bill.

On the day that I was at East 72nd Street - other posts from that trip HERE, and HERE - the bird in the center left of the photo grabbed everyone's eye. For one, it is already in its breeding finery, with gleaming white head and neck, none of the dirty brown mottling that winter-plumaged Herring Gulls should still be retaining.

There was much debate about its identity, and we'll come back to that momentarily.

This fellow sticks out like a sore thumb - an adult Lesser Black-backed Gull, with its charcoal-gray mantle. The only likely source of confusion on Lake Erie, barring oddball hybrids, is Great Black-backed Gull. But adult Great Black-backeds are nearly black above, significantly larger, and do not develop the copious brown mottling on the head and neck.

Lesser Black-backed Gull is essentially part of the Herring Gull complex, and this closely allied species regularly hybridizes with Herring Gulls. Ohio did not record its first Lesser Black-backed until 1977, but the numbers of this European species have skyrocketed since. Along with them have come more records of apparent hybrids.

Back to the weirdo bird of two photos ago. Here we have the Lesser Black-backed Gull bookended by two Herring Gulls, and Mystery Gull is in the backdrop. This juxtaposition of these animals allows us to carefully compare mantle color. The Herrings are the palest gray, the Lesser Black-backed is jarringly dark in comparison, and Mystery Gull is somewhat in between.

At the time, in the field, we felt that it must be a hybrid, possibly between Lesser Black-backed and Herring. Later, I saw a note posted to the Ohio Birds Listserv by John Pogacnik, who was there later and saw the bird. John put forth the theory that it might be a Vega Gull, which is a largely Asian subspecies of the Herring Gull, and is treated as its own species elsewhere in the world.

I delved into the literature, and agreed that John might be onto something. The Kodak Gray Scale is used as a gauge for determining mantle color in gulls to a somewhat exacting degree, and according to Steve Howell in his book Gulls of the Americas, Vega Gull should read a 7-8 on the Kodak scale, versus a 4-5 for (American) Herring Gull. That seemed to match our bird.

However, there seemed to be problems with pigeonholing this animal as a Vega Gull. For one, it appears to have a mostly pale eye - Vega should be mostly dark - and the mantle is probably a bit on the dark side. What to do?

Find an expert. A major shortcoming for us who spend most of our time in the midwestern U.S. is that we just don't see or gain familiarity with Vega Gull. John pointed me to an excellent article detailing the Vega Gull, HERE, by Chris Gibbins. Dr. Gibbins spent time looking at scores of Vega Gulls in Japan, where they are common, and exhaustively documented and described what he saw.

I sent Chris a series of images of our mystery bird, and received a reply in short order. In a nutshell, he did not think it to be Vega, due to the darker mantle, pale eye, and wing pattern. He also noted that, if it were a Vega, it should still have a dirty brown head and neck as the bird still should be in winter plumage. Perhaps most importantly, his overall initial impression was not of a Vega Gull, and that means something coming from someone who has taken the time and effort to carefully study the species in the field.

So, to us at least, the gull remains a mystery. Here it is again, sandwiched between an adult Herring Gull, and an adult Great Black-backed Gull. I find the mystery bird to be very bull-necked in appearance and fairly stout overall - could one of its parents be a Great Black-backed Gull, if not a generation or two removed?

Sometimes, and this is very dissatisfying to some of us birders, a label just cannot confidently be placed on certain birds. But perhaps you know what this Mystery Gull is. If so, please do tell.

When stumped by oddball Herring Gulls and their ilk, I can take solace in this quote from Steve Howell's Gulls of the Americas: "The Herring Gull complex... constitutes one of the most problematic issues in contemporary avian taxonomy". Couple that statement with the large white-headed gulls' penchant for mating with other species, and we sometimes end up with weirdo birds that'll drive you up the wall.

I promise to steer clear of gulls for a while.

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5 comments:

Scott Namestnik said...

Hey Jim. Were you able to see what color the legs were on your mystery gull? I certainly don't claim to be a gull expert, but have you ruled out "Chandeleur" Gull (Kelp x Herring Gull hybrid)? Northern Indiana and southwest Michigan birders have been seeing what they're calling a "Chandeleur" Gull for several years, and at least to my untrained eye the photos (such as the one at http://www.jkcassady.com/gallery/oddgull.htm look similar to your mystery bird.

Andy Avram said...

We saw a similiar gull today at Eastlake. It was a couple shades darker than the surrounding Herrings, and a size bigger (nearly approaching Great Black-backed in size). It was far off and I did not notice if the head was pure white or not. One suggestion put forth was a Great Black-backed x Glaucous Gull.

Same gull? Who knows, but interesting nonetheless.

Jim McCormac said...

Hi Scott, interesting bird! Definitely not the same as the one in this post, though - leg color and head structure are quite different.

Supposedly there are a few records of Glaucous x GBB Gull, but their breeding ranges just barely overlap, so such a thing would certainly be rare!

Scott Namestnik said...

Glaucous x GBB have also been suggested along Lake Michigan...

Jim McCormac said...

Here's what the Birds of North America monograph on Glaucous Gull says: "Larus hyperboreus hybridizes with L. marinus, the Great Black-backed Gull of the n. Atlantic, on occasion, with apparent hybrids observed in Ireland (Wilson 1951) and Newfoundland (B. Mactavish pers. comm.)"

Maybe we just have to start collecting these weird gulls! (joking, sort of)