Saturday, January 30, 2010

Does size matter? Part 1

The age old question.

In Larusology I think nothing can lead you further down the garden path than placing to much importance on the size of an individual bird. It strikes me that at least in the east there is very significant variation in size among the mid-sized Larus sp. (Herring, Lesser-black Backed, Thayer's, Iceland) with seemingly less variation in the larger sp. specifically Great Black-backed and Glaucous.

On checking this impression with the measurements in Olsen & Larrson, Gulls of North America, Europe and Asia I found partial validation for my theory with wide variation in all the regular large gulls. The following are the extremes in measurement using skins of various species considering both sexes (with the exclusion of wt. for Herring& Lesser Black-backed with only females included).

Great Black-backed Gull  Wing 445-520mm Wt. 1033-2272g
Glaucous Gull                   Wing 408-510mm Wt. 946- 2215g
American Herring Gull     Wing 412-468mm  Wt. 600- 1240g
Lesser Black-backed Gull  Wing 383-456mm  Wt. 620-1100g
Thayer's Gull                     Wing 384-442mm  Wt. 712- 1002
Kumlien's Gull                  Wing 380-442mm Wt. 530-970g

As you can see the largest Kumlien's Gull overlaps with the smallest Glaucous with broad overlapping of the four mid-sized species. Surprisingly (at least to me) the mean wing length for male Kumlien's was near identical to male Thayer's. The weight for a female Thayer's was however significantly higher than even the male Kumlien's attesting to its more robust structure.

The centre bird in the following picture is a great example how size of an individual bird can cause significant confusion in determining its identity. Initially I thought this was a Glaucous Gull but then I noticed the dark pigment on the primaries. I then started thinking Nelson's Gull especially as the primary projection seemed a bit short. Finally after extensive study both in the field and of the pictures and after going back and forth on a couple of occasions I came to a final definitive conclusion that it was a Kumlien's Gull

A very large adult male Kumlien's Gull

If just this one picture was available you would have a very hard time convincing me this is a Kumlien's Gull. It was as robust as most of the Herrings and larger than many. Its head is rather Herring Gull like in this posture.

Large adult male Kumlien's Gull with seemingly short primary extension

Then I looked hard at the head and bill structure in a few of the shots and I thought- this has to be a Kumlien's Gull.

Adult Kumlien's Gull head close-up

Juvenile Nelson's Gull head close-up

Adult Glaucous Gull head close-up

The top picture shows the classic dove-like head with relatively small bill so typical of Kumlien's Gull.

After reviewing the open winged shots it was clear P10 was not yet fully grown and this probably accounted for the shortish primary extension. It was also entirely clear that the primary pattern was near identical to Howell & Mactavish, 2003 -variation e wingtip pattern for adult Kumlien's Gull- Alula 9: 2-15. The illustration of these variations by Martin T. Elliot can be seen in Howell &Dunn pg. 252.

Adult Kumlien's Gull open-winged

Adult Kumlien's Gull in flight

This left no doubt in my mind that this was a Kumlien's Gull - just a real hefty one.  Even though I had noted in the past that Kumlien's Gull  was quite variable in size with the odd bird of Herring Gull size this bird through me off and it took quite a bit of study before I was convinced of its identity. The main variable that created the confusion was clearly its size

If this bird had conformed to my mental image of the classic size and structure of Kumlien's Gull (as do the following birds) I very much doubt I would have had a moment of doubt.

Second winter Kumlien's Gull

Adult winter Kumlien's Gull

Third winter Kumlien's Gull

Adult winter Kumlien's Gull

Second winter Kumlien's Gull

We need to remember that not all birds are going to be "classic" and a significant number of outliers
are waiting to lead you down the garden path. Following are a few more robust Kumlien's.

Juvenile Kumlien's gull

Second winter Kumlien's Gull

Second winter Kumlien's Gull

Juvenile Kumlien's Gull

Juvenile Kumlien's Gull       First winter Herring Gull

In comparing the first and second groups of Kumlien's Gulls there is clearly structural differences with the later group having more Herring Gull like heads and a somewhat more generous bill size. My suspicion is this is entirely based on sex the former birds being female and the later male. 

I will continue this theme in my next post by examining the variation in size and structure of Thayer's Gulls.

To be continued............


Friday, January 15, 2010

Gulls at Gambell

 I suspect right at the moment there is probably little more than the occasional Raven floating around Gambell. In the late spring however a fairly wide variety of breeding and migrant gulls can be found around this Alaskan outpost. Being located in the Bering Sea just 38km from Siberia obviously the resident gulls have a distinctly Eurasian flavor with the migrants being mostly high arctic nesters.

Siberia as seen from Gambell across the Bering Sea

The Yupik village of Gambell is on the north western tip of St. Lawrence Island and has been a mecca for ABA birders for over 25 years. Although conditions were originally very rustic they are now very decent. A variety of tour companies lead trips to Gambell and because of the very complicated logistics I would suggest this is certainly the easiest if not the cheapest way to bird Gambell. I travelled to Gambell as well as Nome, Adak, Barrow and the Pribolofs last spring with High Lonesome and it was a great adventure with great leaders and excellent organization and support. Accommodations and meals were great (considering the locations) on all parts of the trip. Birding Alaska is always a bit of a crap shoot given the weather and off beat locations. Stories of people being stranded in various places abound and I felt I was lucky to have only experienced a few short delays.

Whale bones and seal meat at Gambell

Going to Gambell is more than just a birding trip it is a fascinating cultural experience. The relationship between the birding community and the Yupiks is very interesting and complex. Given that one can easily stay out to 2 AM not only birding but taking pictures Gambell can be exhausting especially for the more obsessed types such as myself. Luckily no matter how late you stay up you will have lots of company as the Yupiks- adults and children make good use of there brief spring/summer.

Yupik family on 4 wheeler around 2:00 AM

The best spot for studying gulls at Gambell is at the sea watch. On some occasions giant icebergs loaded with roosting gulls would roll by like floats in a parade. Glaucous Gulls are probably the commonest species followed by the local "Herring" Gull which I will refer to subsequently as Vega Gull.

Parade of gulls at Gambell sea-watch including Glaucous, Vega and Slaty-backed

According to Howell and Dunn the subsp. of Glaucous Gull on the Bering Sea Islands is pallidissimus. Barrovianus is found on mainland Alaska while to the east in the Canadian arctic hyperboreus (which is felt to be a seperate subsp.- leucretes by some) the nominate subspecies is native. Pallidissimus averages the palest and largest of the subsp. The differences between these subsp. are subtle.

Adult Glaucous Gull in high breeding plumage

Although one often has other things on your mind (like seeing the Green Sandpiper before one of the native kids clips it with his .22) at Gambell I did spend some time studying the commoner breeding sp. It was great to see the Glaucous Gulls in high breeding plumage - probably something you will never see at home (unless you live on Baffin Island).

Adult Glaucous Gull in high breeding plumage

The above pictures illustrate the characteristic Glaucous Gull features present during high breeding season including the lemon yellow to yellow-orangish eye, the orange to pinkish-orange orbital ring. the pink-flesh coloured gape and the deep orange bill with red gonys. A real stunning combination.

Adult Glaucous Gull in high breeding plumage

Vega Gull  known taxonomically according to the AOU ( and the relatively liberal BOU) as Larus argentatus vegae and by others as Larus vegae is a very localized breeder in North America breeding regularly only on St. Lawrence Island. Gambell is one of the few North American birding sites were one can study numbers of this taxon. It is common in the late spring.

Adult Vega Gull with adult Glaucous Gulls

It was somewhat of a disappointment that the overwhelming majority of the Vega Gulls present were adults in breeding plumage about the least likely version to end up straying into our territory. I did not see a single first cycle bird unfortunately.

Adult Vega Gulls in flight

The adult Vega Gull is relatively simple to differentiate from L.a. smithsonianus  with its dark black eye, and significantly darker upperparts (Kodak 7-8 vs. 4-5). Subtler difference include an orangish-red orbital ring in vegae as opposed to a yellow- yellowish-orange in smithsonianus along with minor differences in the primary patterns and of course the leg/foot color.

American Herring Gull ( L.a. smithsonianus )-high breeding plumage

Vega Gull (L.a. vegae)- almost high breeding plumage

The above photos illustrate nicely the clear difference in the color of the orbital ring between these two taxon.

The wing and primary pattern differ in a couple of definitive ways other than just the shade of gray. Vega Gull clearly has a broader trailing edge that merges into a "string of pearls" (white tongue- tips) at the inner primaries. This is very similar in effect to the sympatric Slaty-backed Gull. Although the white tongue-tips may be seen in American Herring Gull ( see second example below) the amount of white is usually quite reduced.

Adult Vega Gull- wing closeup

Adult American Herring Gull - wing closeups

Adult Vega Gull- wing closeup

Adult American Herring Gull - wing closeup

On to the legs. Once again Vega seems to share another trait from Slaty-backed Gull. This is quite a fascinating phenomena and I wonder if this is based on convergent evolution. The Vega Gull has deep pinkish red feet with lighter pink legs. Much brighter and more saturated than any other of the "Herring" Gulls.

Adult Vega Gulls showing bright reddish pink feet and legs

Adult American Herring Gull showing dull pink feet and legs

The third large Larus species to be found on St. Lawrence Island is  L. schistisagus more commonly known as Slaty-backed Gull. Howell & Dunn noted breeding in the Western Aleutians and at Cape Romanzof but not on the Bering Sea Islands. They mention it is locally uncommon on St. Lawrence Island and the Seward Pennisula in the fall. Numerous birds were present during my visit including several adults and a third cycle bird.

Adult Slaty-backed Gull and Adult Glaucous Gull

I remember a discussion line on ID Frontiers last year in which Gary Rosenberg commented on the universally very dark-mantled Slaty-backed Gulls in Alaska and expressed concern that the lightness of the mantle of several of the birds identified in the Lower 48 seemed out of range in his experience. After viewing several adult Slaty-backeds in Gambell I can see his point. These birds are very dark- backed. Ujihara talks about the real variation and the confounding variables in this trait on his website:

The Vega Gulls also appear very dark in Gambell and at first glance it is easy to think these are Slaty-backeds. I suspect Gambell Slaty-backeds are at the dark end of the spectrum and that the usual light conditions at Gambell intensifies the effect. Note how dark the Vega Gulls in the following photo appear   and the Slaty-backs appear jet black.

Slaty-backed, Vega and Glaucous Gulls

I have include some Slaty-backed flight shots

Adult Slaty-backed Gulls in flight

Third year Slaty-backed Gull

Like the Vega Gull the Slaty-backed has bright pinkish-red feet however Vega Gulls seem to have darker red feet and duller pink legs at least in breeding season while the Slaty-backeds seem to have the same bright pinkish -red colour to both feet and legs.

 Slaty-backed Gulls have a reddish orbital ring very similar to Vega. Of course the Slaty-backed Gull has a very light eye usually with a yellowish tinge in breeding plumage while the Vega Gulls eye is usually very dark.

Third year Slaty-backed Gull showing bright pink feet and legs

Adult Slaty-backed Gull showing lemon yellow eye and reddish-orange orbital ring

I had been in Gambell for about 5 days and had yet to spend any real time photographing gulls. I was heading back from the sea watch that evening around 10:30 pm when I noted a feeding frenzy of gulls just offshore.  I thought this would be a nice opportunity to get some flight shots and headed to the party.
I was there for 15-20 minutes when out of the blue an adult Ivory Gull swooped in a joined the frenzy. It was fluttering about just off shore as I tried to calm myself to get some pictures.

Adult Ivory Gull

It wasn't long before I realized that I was in a bit of a "situation". I was actually one of the few people in our group who had seen an Ivory Gull. Here I was about 20 minutes away from the lodge with no radio and an Ivory Gull at arms length. I could imagine the reception when I recounted the story and shared the pictures with the group. Just as I decided I better head back and raise the group and flottilla of ATVs crested the hill and I waved the group over. Apparently the Ivory Gull had swooped by the sea watch on the way to the feeding frenzy and had been reported back to the group. Saved by the bell.

Adult Ivory Gull

It put on a good show for the group then vanished never to be seen again at least by us.

We saw two other gull species during our time at Gambell. Black-legged Kittiwake was a fairly regular fly-by at the sea watch and an adult breeding plumage Black-headed Gull spent a day and a bit south of the lake but was never within distance for photographs. We didn't see a Sabine's Gull but I believe it is a regular migrant. To my disappointment we did not see a Ross's Gull. It is not to be expected at Gambell but should always be hoped for.

I thought I would share a few more gull pictures from various Alaskan destinations to finish off:

First cycle and Adult Black-legged Kittiwake- Little Tanaga Strait, Aleutians

Adult Galucous-winged Gull- Little Tanaga Strait, Aleutians

Adult Mew Gull- Anchorage

Adult Mew Gull- Anchorage

Adult Sabine's Gull- Barrow

Adult Black-legged Kittiwake- St. Paul Island

Adult Red-legged Kittiwake - St. Paul Island

Adult Red-legged Kittiwake - St. Paul Island

Adult Red-legged Kittiwake - St. Paul Island

First cycle and Adult Red-legged Kittiwake - St. Paul Island

First cycle and Adult Red-legged Kittiwake - St. Paul Island

Red-legged Kittiwake was the technically (given the current taxanomical status of Vega Gull) the only "lifer" gull I saw in Alaska and I enjoyed it immensely. Its a most unusual bird with the most restricted breeding range of any gull. Traditionally most of the world population nested on St.Paul and St. George Islands (the Pribilofs). According to Dunn & Howell the population in the Pribilofs has declined by as much as 50% since the mid 70s. Inversely populations in the western Aelutians have been on the increase.

There were no Ross's Gull at Barrow either. I also missed Kamchatka Gull ( L. (canus) kamtscatschensis) the Siberian version of the Mew Gull considered by many authorities to be a distinct species. I am hoping to see the Kamchatka Gull next spring somewhere between Adak and Attu. If anyone wants to come along there may be a spot left on the boat - talk to John Puschock for the details.

Kirk Zufelt