Monday, February 27, 2017

If It Looks Like a Thayer's Gull

Gulling

Gulls are often one of the last species group that birders pay attention to. Individual variation, large plumage differences between ages, sexual dimorphism, plumage abnormalities, clinal variation, the effects of bleaching and wear and even as yet unresolved taxonomy issues all combine to create a bit of a mess.

Back in 2014, I vowed to look through the thousands of gulls at Dennis Point Wharf in Lower West Pubnico until I found a first-cycle Lesser Black-backed Gull. I had previously spotted adults of this species, but while birds of the year are seperable from our more regular large, white-headed gulls, the differences are more subtle. These minute differences in feather pattern, bare part colour, size and shape are what gulling is all about. For the last 3 winters I've been spending hours and hours looking at gulls. This group of birds is fairly unique in that most of the time in the field is spent actually looking at birds, not looking for birds.


More Questions than Answers

The American Ornithological Union's 57th supplement lists Thayer's Gull (Larus thayeri) and Iceland Gull (Larus glaucoides) as distinct species, Iceland Gull comprising the Kumlien's Gull (Larus glaucoides kumlieni) and nominate (Larus glaucoides glaucoides) subspecies.

The taxonomic issues surrounding Thayer's Gull and Iceland Gull are still being discussed. I suggest that you read Taxonomic History of Thayer's Gull, a 1999 article in Ontario Birds by Ron Pittaway.  Our innate need for classification of what we see becomes difficult in the case of these taxa. McLaren (2012) suggests that Thayer's Gull might best be treated as the dark extreme of a single species with Kumlien's Gull as the variable result of interbreeding with Iceland Gull. Earlier works such as Webber (1981) and Godfrey (1986) as well as a recent blog post named Thayer's the Iceland Gull - One Species by Amar Ayyash also suggest that the three taxa listed above should be conspecific:

Iceland Gull (Larus glaucoides glaucoides)
Kumlien's Gull (Larus glaucoides kumlieni)
Thayer's Gull (Larus glaucoides thayeri)

In the above classification, L.g. glaucoides becomes the nominate subspecies simply because it was described first by Meyer in 1822. Kumlien's Gull was first described in 1883 followed by Thayer's Gull in 1915.

A recent discussion on the North American Gulls Facebook Page prompted a few heavy hitters in the birding world to give their two cents. Steve Hampton, Bruce Mactavish, Peter Adriaens and Christopher Gibbins appeared to prefer the 2-species solution with Kumlien's Gull as the hybrid between Thayer's and Iceland. Some compared these species with the species pairs of Glaucous-winged Gull & Western Gull or Blue-winged Warbler & Golden-winged Warbler with their respective hybirds the Olympic Gull and Brewster's Warbler. Independent of the opinions shared by the participants, all could agree that more research is needed.

Pittaway's 1999 taxonomic history paper concluded with, "Regardless of how we classify them, they are no more or less identifiable in the field."

The apparent clinal variation from from the dark-eyed, dark-winged, less gentle proportioned Thayer's Gull to the pale-eyed, white-winged, smaller-billed and more gentle looking Iceland Gull definitely does make identification of extralimital birds difficult. I think most would agree that if it looks like a Thayer's Gull, then we can assume that this is likely linked to its provenance and/or its genetic makup. Given the current taxonomic classification of Thayer's Gull as a separate species, if a bird in Nova Scotia is found to tick all of the boxes, I wouldn't hesitate to label it as a Thayer's and add it to your Nova Scotia list as a full species.


The Pubnico Thayer's Gull

Paul Gould and I were test driving my new-to-me Subaru Forester on January 8, 2017 when we spotted a great Thayer's candidate at Dennis Point Wharf in Pubnico, Yarmouth County. We snapped a few photos and made sure to get some views of the open wing.

Here is a photo from our first encouter with the Thayer's Gull at Dennis Point Wharf in Pubnico, Nova Scotia, January 8, 2017. Photo by Alix d'Entremont.

I didn't realize exactly how many boxes this bird ticked until I reviewed the photos at home. Here are a few reasons why this gull fits perfectly for a Thayer's Gull:

-The black on the outer primaries when viewed from above is as dark as the adjacent Herring Gulls;
-P10 has dark subterminal marks;
-The outer web of P9 is completely dark;
-There is an almost complete dark subterminal band on P5;
-The iris was dark (contrast between the pupil and iris was only visible in direct sunlight);
-The orbital ring is a deep pinkish colour;
-The head, neck and breast show a extensive blotchy brown pattern;
-The bill base is greenish-yellow;
-The legs are a pale raspberry.

This image shows well the primary pattern of the Thayer's Gull at Dennis Point Wharf in Pubnico, Nova Scotia, January 14, 2017. P10 has dark subterminal marks between the mirror and apical spot; the outer web of P9 is completely dark; there is an almost complete dark subterminal band on P5. Photo by Alix d'Entremont.

Here we get a look at the pale underside of the outer primaries of the Thayer's Gull at Dennis Point Wharf in Pubnico, Nova Scotia, January 14, 2017. This is quite different from that of a Herring Gull. Photo by Alix d'Entremont.

This image allows for comparison of a Herring Gull with the Thayer's Gull at Dennis Point Wharf in Pubnico, Nova Scotia, January 14, 2017. Note how the black on the outer primaries is of equal darkness on both gulls. The Thayer's shows a dark eye and greenish-yellow based bill in contrast with the pale yellow iris and orangish-yellow based bill of the Herring. Photo by Alix d'Entremont.

Here we see the pale raspberry legs of the Thayer's Gull at Dennis Point Wharf in Pubnico, Nova Scotia, January 14, 2017. Photo by Alix d'Entremont.

This bird is immediately recognizable with the naked eye both in flight and on the water. The combination of features, most notably the dark eye, extensive hood and primary pattern are unique among the thousands of gulls at Dennis Point Wharf. It should be noted that there are many imposters as well. Kumlien's Gulls can show one or two Thayer's-like features like dark eyes, dark wings and an extensive hood, but only this bird has been found to show all of these features.

I observed this bird 4 times during January and then we were in for a great surprise when Mark Dennis spotted this exact individual at West Head on nearby Cape Sable Island, Shelburne County, on February 1, 2017. We confirmed that it was in fact the Pubnico bird because both birds had a small portion of the inner web of P5 on the left wing missing. It was then refound in Pubnico on February 4, again at Cape Sable Island on February 10 and once more in Pubnico on February 25.

The Thayer's Gull at Dennis Point Wharf in Pubnico, Nova Scotia, February 4, 2017. Photo by Alix d'Entremont.

The Thayer's Gull at Dennis Point Wharf in Pubnico, Nova Scotia, February 4, 2017. Photo by Alix d'Entremont.

The Thayer's Gull with two Kumlien's Gulls (adult and first-cycle) at Dennis Point Wharf in Pubnico, Nova Scotia, February 4, 2017. Photo by Alix d'Entremont.

References:

Godfrey, W .E. 1986. The Birds of Canada. Revised Edition. National Museums of Canada, Ottawa.

McLaren, I.A. 2012. All the Birds of Nova Scotia: status & critical identification. Gaspereau Press Ltd, Kentville, N.S., Canada

Pittaway, R. 1999. "Taxonomic History of Thayer's Gull". Ontario Birds 17(1):1-13.



Weber J.W. 1981. The Larusgulls of the Pacific Northwest Interior, with

taxonomic comments on several forms (Part 1). Continental Birdlife 2(1): 110.

Saturday, December 31, 2016

2016 Year In Review - The Rarities

This post is a synopsis of the interesting birds that I saw in 2016 as well as a list of the lifers for the year.

We had our first confirmed provincial record of Kamchatka Gull that stayed in Meteghan during February and March. Spring of 2016 was notable due to the large number and variety of shorebirds, for example, I saw my first spring Stilt Sandpiper and American Golden Plover. I found my first singing Northern Waterthrush likely on territory in Yarmouth County. We confirmed another pocket of breeding Veerys for Yarmouth County at the Hebron Recreation Complex. The number of sites that I know of with Canada Warblers during breeding season in my end of the province continues to rise (I just wasn't paying enough attention before). Fall 2016 didn't see an influx of western birds like the previous year. My father photographed the provinces 2nd record of Calliope Hummingbird in my yard, a bird that I didn't get to see. I was witness to the unprecedented numbers of Cory's Shearwaters near the mainland during September and October. A photo that I had taken back in 2012 in my yard was identified this year as a Rock Wren representing only the 2nd record for the province.

Lifers that were long overdue were Green Heron, Black Tern and Pine Grosbeak (I still don't have Spruce Grouse!). My total lifers this year was 13, down from the 22 during 2015 (see 2015 review here). I ended the year seeing 260 species in Nova Scotia.

Here is the list of the 13 lifers for 2016. Self-found birds are annotated with an asterisk (*). The links associated with the items in the list bring you to the appropriate blog post or if I didn't blog about it - the eBird Checklist.

1. Green Heron
2. Curlew Sandpiper
3. Gray-cheeked Thrush
4. Common Gallinule
5. Sandwich Tern
6. Black Tern
7. Northern Rough-winged Swallow*
8. Yellow-billed Cuckoo
9. Cerulean Warbler (*, sort-of)
10. Least Bittern
11. South Polar Skua
12. Pine Grosbeak
13. Pink-footed Goose

Below are some of the memorable birds that I photographed during the year.

Mountain Bluebird, Cape Sable Island, Jan 1, 2016.
Snow Goose in Yarmouth, January 8, 2016.
Abnormally coloured Common Grackle, Tusket, Feb 5, 2016.
Red-shouldered Hawk, Pleasant Lake, February 7, 2016.
Abnormally coloured European Starling, Yarmouth,  Feb 7, 2016.
Snowy Owl, Cape Sable, March 28, 2016.
Wintering Cape May Warbler, Argyle, April 4, 2016.
Pine Warbler, Pubnico, April 16, 2016.
Summer Tanager, Woods Harbour, May 6, 2016.
Green Heron, Pubnico, May 6, 2016.
Stilt Sandpiper, Cape Sable Island, May 7, 2016.
One of two Curlew Sandpipers, Cape Sable Island, May 7, 2016.

Gray-cheeked Thrush, Chebogue, May 8, 2016.
Indigo Bunting, Cape Sable Island, May 15, 2016.
Orchard Oriole, Cape Sable Island, May 15, 2016.
Little Blue Heron, Pubnico, May 15, 2016.
Common Gallinule, Cape Sable Island, May 25, 2016.
Glossy Ibis, Cape Sable Island, May 25, 2016.
Willow Flycatcher, Yarmouth, June 6, 2016.
Red-necked Phalarope, Pubnico, May 17, 2016.
Sandwich Tern, Pubnico, July 13, 2016.
Black-billed Cuckoo, Pubnico, July 13, 2016.
Yellow-crowned Night-Heron, West Green Harbour, July 13, 2016.
Ruff, Amherst, July 22, 2016.
Black Tern, Amherst, July 22, 2016.
Northern Rough-winged Swallow, Chebogue Pt, August 3, 2016.
Cory's Shearwater, German Bank, August 13, 2016.
Manx Shearwater, German Bank, August 13, 2016.
Buff-breasted Sandpiper, Cape Sable, August 27, 2016.
Cape May Warblers, Bon Portage Island, August 28, 2016.
Cerulean Warbler, Bon Portage Island, September 3, 2016.
Red Knot, Peases Island, September 4, 2016.
Philedelphia Vireo, John's Island, September 10, 2016.
Least Bittern, CSI, September 16, 2016.
South Polar Skua, Bay of Fundy, September 24, 2016.
American Golden Plover, Cape Sable, October 1, 2016.
Yellow-breasted Chat, Pubnico Pt, October 2, 2016.
Prairie Warbler, Pubnico Pt, October 2, 2016.
Cooper's Hawk, Pubnico Pt, October 31, 2016.
Clay-colored Sparrow, Pubnico Pt, November 2, 2016.
Red-bellied Woodpecker, Tusket, November 18, 2016.
Red-headed Woodpecker, West Pubnico, November 19, 2016.
Black-headed Gull, Meteghan, November 20, 2016.
Pink-footed Goose, Cape Jon, November 24, 2016.
Lark Sparrow, Canso, November 25, 2016.
Greater White-fronted Goose, Yarmouth, December 19, 2016.