Friday, December 18, 2009

Kumlien's Gulls of St.John's

I've spent quite a bit of time at our sewer outflow in St.John's this fall/winter, observing the more than 1000 Kumlien's Gulls that can be seen there, at very close range everyday. St.John's is the best location in the world to observe this subspecies of Iceland Gull. I'm particularly interested in studying the variation in Kumliens Gull,which seems endless, at least in regards to their wintip variation, from very black, to almost pure white wing tips.

However,not all characters are this variable. Almost all Kumliens Gull have quite a rounded head and a slight short bill,especially in comparison to Herring Gull,which show a more sloping foredead. The majority of Kumliens are pale eyed,with some as pale as Herring Gull.There are others that have eyes of dark amber, with or without dark spotting.Sometimes the eyes are medium to dark brown. Most have extensive head streaking (often appearing more smudgy in comparison to Herring Gull),while occasionally there are birds that appear quite white headed.However,upon closer inspection, these birds often have a very light brown wash over the head and neck. Invariablym Kumliens have a purple orbital ring,sometimes appearing a light pink/purple.On some birds the orbital ring can very difficult to seem even at very close range. These birds often show only a slight purple pink wash in the orbital ring,just in front of the eye.

Kumliens are very consistent in mantle shade (in my experience) with the overwhelming majority being a shade paler than the average Smithsonianus Herring Gull.On rare occasions, there are birds that appear noticeably darker above than surrounding ICGU's and closely match Herring Gull in mantle color. In my experience these birds often show the most extensive dark in the wing tips as well.

Speaking of wing tips,this is where Kumliens Gulls really get out of whack. The extensiveness of black coloration in the outer primaries is extremely variable. It can range from almost pure white, to being extremely close to Thayer's Gull. These "pseudo Thayers" have medium black coloration on the outer webs of the outer 4 primaries and some even have a small grey mark( always paler than the dark markings in the outer 4 primaries,in my experience) on p5!. With such a high degree of variability it becomes very difficult to conclusively identify a true Thayer's Gull in Newfoundland- the opposite being true in California. We seem to get a few birds each winter that look like good Thayer's Gull 'candidates' in terms of plumage, but these birds are often very slight and look identical to the surrounding Iceland Gulls in structure. As well,particularly in adult birds, there are often other characters that are less then perfect, e.g.eye color,mantle shade,head streaking and most often wingtip pattern.

Essentially, in Newfoundland we are looking for the prototypical Thayer's Gull. For me, this is really the only correct way.Since there seems to be a direct cline from Thayer's to Kumliens,how can one decide where Thayer's ends and Kumliens begins or vice versa? For Thayer's, we need a nice big male with lots of dark brown head streaking,a dark eye,mantle shade at least as dark as Smithsonianus(if not darker) and overall structure tending closer to Herring Gull than an average Iceland Gull. In the wingtips things become a little more complicated. Ideally, p10 would have at least a partial black sub terminal bar, p9 would have a completely black outer web,not interrupted on the outer edge by a white mirror, p8-6 with extensive black outer webs and ideally a black mark if not a broken or full bar on p5. Also, the primaries would be almost jet black with folded wingtip coloration very close to Herring Gull.
Below you will find a series of dark winged presumed Kumliens Gulls all photographed on the same day in St.John's. I will be adding to this collection (especially spread wing shots) in the coming days.




A slight bird. Greyish black wingtips.Note the very rounded head,short bill and very pale eye.



Wingtips appearing quite black but note how much paler they look below. Slight pale brown wash to head,appearing almost white headed from a distance. Slightly less rounded head than the above bird and bill appering slightly larger- perhaps a male?



Wing tip coloration seems pale for Thayer's and note the white mirror that interrupts the black outer web of p9.Note also black markings on p6-p10.





This is perhaps the most Thayer's like Kumlien's Gull possible? Overall this bird has many THGU like feature,but structurally is still very ICGU like and the wingtips seem pale for THGU as well.UNfortunately I never saw this bird fly.




Typical Kumliens Gull structure. Greyish wingtips,not how the mirror on p9 interrupts the grayish black outer web. THGU can show a wing pattern very similar to this,but the primaries are more extensively black.

Next are two birds that are perhaps more comlicated than those above. Any comments on these two birds are very much welcomed.



Bird #1. A good THGU candidate.Wing tip,although lacking a black mark on p5, the extreme outer web of p9 is black, with the middle portion of the black outer web interrupted by a 'mimi mirror' that is separated from the main mirror by the dark feather shaft. I've seen photos of THGU from CA. that match this bird almost exactly.

pbase/image/574319



Bird #2. A somewhat confusing individual.









Surely this is out of range for Kumliens,but what is it??

On a different note, in anticipation of some birding with an American visitor, I went to see Great Cormorants at a super top secret location near the battery. I got this ok photo of a Great Cormorant sitting on a post.



Great Cormorant

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