Bob Yukich writes:
On January 2, 1999 I was birding the Toronto waterfront with Juha Varrela, a friend from Finland who was visiting over the holidays. We were just finishing up a morning's birding, and were looking over the gulls and waterfowl at Sunnyside before our return home. At about 1200 hrs., as we approached from the west, we saw a small group of gulls sitting on the ice inside the breakwater between the foot of Ellis Ave. and Colborne Lodge Dr. While they were still in the distance, I raised my binoculars to give them a quick scan before approaching any closer. The majority appeared to be Herring Gulls Larus argentatus, but I immediately noticed a dark-backed gull amongst them which I thought was a Lesser Black-backed Gull Larus fuscus, because it had a lot of dark streaking on the head. I pointed it out to Juha, and we continued walking towards it until we were almost opposite the spot where the gull rested.
We were now fairly close to the bird and, looking again through my binoculars, I could see it sitting on the ice, its legs hidden from view. It appeared to be an adult gull in winter plumage. The mantle looked too dark, and the smudge around the eye didn't seem dark enough, for the "graellsii" race of Lesser Black-backed Gull. I began to think that it was just a Great Black-backed Gull Larus marinus, but that wasn't right either, not with all the dusky streaking on the head. Next I thought of the "intermedius" race of Lesser Black-backed Gull. The mantle colour was perfect for it. However, this gull looked too large, about the same size as nearby Herring Gulls, and the overall structure, especially the head and bill, was not right for any race of Lesser Black-backed Gull. Juha was very familiar with all of those races from Europe, and especially from Finland. He also had experience with many of the darker "Old World" races of Herring Gull, but this bird did not match anything he was familiar with.
I began to think that it might be a hybrid. Whatever it was, it was good! I asked Juha if he had his camera, and said that if he did, he should try to get some photographs of the bird. He responded, and ran to his van to get the camera. Meanwhile I started studying the bird through my scope. I now began to consider Slaty-backed Gull Larus schistisagus after noticing that this bird had quite a large white tertial crescent. I also realized that the chances of this species showing up here were quite remote. Juha returned with his 35mm camera, which he hand-held using a 300mm lens and fast film. Positioning himself as close to the shoreline as possible and opposite the bird, he began taking photographs. I continued studying the bird.
Shortly after Juha began taking pictures, the gull stood up, revealing bright pink legs - a promising sign. It appeared to be the same size as the Herring Gulls it was with, maybe a bit chunkier, and with a similar shaped head and bill. The mantle colour was a dark slate, darker than on the "graellsii" race of Lesser Black-backed Gull, but paler than that of a nearby Great Black-backed Gull; it was intermediate between the two. There was a large white tertial crescent, noticeably larger than that on any of the Herring Gulls, and a large round-shaped scapular crescent, also larger than on any of the nearby gulls. The visible folded black primaries contrasted slightly with the dark mantle. Each primary was tipped with white, beginning with a fairly small apical spot on P10. These spots became successively larger inwardly, through to P6, the white tip of which was often just visible at the edge of the white tertial crescent. At times I could see the underside of the outermost primary, P10. It showed a small white tip with a narrow band of black next to it, followed by a large, oval-shaped white "mirror" that completely covered both webs.
The bill was similar to that of nearby Herring Gulls, moderate in size with little swelling at the tip, and not much gonydeal angle (almost parallel sided). The basal two-thirds of the bill was a chalky yellow, and the tip was a brighter orange yellow. There was a medium-sized red gonys spot on the lower mandible, and a small dusky mark (possibly extending slightly onto the upper mandible) posterior to and touching this spot, suggesting a possible fourth-year bird. The crown appeared rounded or slightly flattish, depending on the bird' s posture. The eye was pale yellow as in Herring Gull. The orbital ring was not noted.
The head, neck and breast were streaked and mottled with grayish browns. The dense streaking around the eye formed a dark eye-patch, extending posteriorly in a point, upwards and towards the rear of the crown. It also extended in a similar fashion in front of the eye, but possibly more bluntly so. This eye-patch was not as dark as is usually seen in adult winter-plumaged Lesser Black-backed Gulls of the race "graellsii". There were short dusky streaks on the crown that continued down the nape, more heavily so down the hind-neck, and darkest on the lower hind-neck. The front and sides of the neck were also streaked dusky, being perhaps more mottled on the lower neck. The underparts were white with large well-spaced mottling across the entire breast. This mottling had a more brownish hue than the rest of the streaking, which was more grayish brown. The tail was all white. The legs were a bright pink, and this colour was matched by a few Herring Gulls with the brightest legs.
After noting as much as I could on the bird, I was hoping to see it fly so that we could see whether it had the diagnostic "string of pearls" pattern of white spots that Slaty-backed Gull shows on the outer primaries. At one point several of the gulls, including our dark-backed bird, flew up briefly and landed almost immediately. Juha was still clicking but wasn't sure whether he had gotten a good flight shot or not. It happened so quickly that I really didn't see much more on the bird. Finally, several of the gulls flew off but our mystery bird remained with a few Herring Gulls. A short time later, after he had taken about 30 exposures, Juha began walking back towards me. Suddenly our gull flew up and eastwards. Juha didn't have time to get another shot, and I tried in vain to see the wingtip pattern as it moved away from us. After flying a short distance, it turned and began coming back towards us. I was hoping that it would fly over our heads so that we could see the pattern on the underside of the primaries, but it veered northward and continued flying over the Gardiner Expressway and High Park, all the while gaining altitude. Finally it disappeared from our view.
When it first flew I had a micro-second view of the underside of the primaries. I sensed they might have had the pattern I was looking for, but I couldn' t be sure. In flight it had a slightly heavy bearing, and the wings did not appear particularly long. Not much else was noted. We then continued walking a short distance in an eastward direction, checking out the various ducks and gulls. After another 15 minutes or so had passed we returned home, but first we checked the gulls sitting on the ice at the south end of Grenadier Pond. Our bird wasn't there.
Juha was returning to Finland in a couple of days and wouldn't have time to get his slides developed here. We agreed that once he had them developed in Finland he would send me duplicates of most of them. We still weren't sure whether he had captured anything on film that we hadn't already seen in the field. After the slides were developed in Finland, Juha e-mailed me saying that he had one good flight shot of the upper wing. After he had compared it with photos of known Slaty-backed Gulls, the primary pattern had matched perfectly. Everything else had matched up also - we were pretty excited!
About a month after having seen the bird, I received the slides. I looked at them carefully and compared them with various photographs of known Slaty-backed Gulls. I also referred to the video "The Large Gulls of North America" with Jon Dunn, which I found especially helpful. I feel that the photographs of this bird match Slaty-backed Gull in every way. The following is a list of characteristics that are evident in these photos, the combination of which rule out any other species.
First, I believe that this gull was probably a female because of its relatively small size and small bill (a Slaty-backed Gull can exhibit much sexual dimorphism). The most important photograph, that of the upperside of the gull in flight, shows well the wide white trailing edge of the secondaries which extends into the inner primaries, much wider than on any of the Herring Gulls in the photo. The wing also shows a conspicuous white leading edge. Most important is the "string of pearls" effect created by the white "tongues" in P7, P6 and P5. These are separated from the white tips on each feather by varying amounts of black. P10 shows a large white "mirror", and P9 and P8 have no "mirror" at all, just white tips. The amount of white in P8 on Slaty-backed is variable; it can sometimes have none at all, as in this individual (there could be a slight mark on the inner web of P8, hidden by the outer web of P7). Difficult to see in this photo, but visible upon close inspection is the gray inner web of the outer primaries (mostly covered by the black outer web of the primary next to it). This feather pattern (black outer web and gray inner web) is right for Slaty-backed Gull.
Also evident in this photograph are the wide-based wings, noticeably wider than on any of the Herring Gulls in the photo, another feature of Slaty-backed Gull. The dense streaking around the eye comes to a point behind the eye, and somewhat so in front of the eye, also a feature of Slaty-backed. In the photograph of the standing bird the pink legs are visible. Also evident in the same photo is the deeper chest and longer (and thicker) neck of this gull, when compared to the Herring Gull next to it. These are all characteristic of Slaty-backed Gull. The pale yellow eye is difficult to see in any of the slides. The wide white tertial crescent and large scapular crescent are also visible in the slides that show the standing or sitting bird. I have included a slide which shows a Great Black-backed Gull behind the Slaty-backed Gull, for comparison. Their mantle colours appear similar in this photograph due to the lighting, although the Slaty-backed Gull did in fact have a somewhat paler mantle.
The mantle colour of this bird also rules out any race of Western Gull Larus occidentalis. The darker southern race of this species wouldn't be quite as dark, and would never show this amount of dusky streaking. None of the "Old World" races of Herring Gull would be as dark as, or have the combination of features that this bird had. "Vega" Herring Gulls would always be paler mantled. Hybrids could be a difficult matter, but I don't think any would show the combination of head streaking and various other features that this bird exhibited. Everything in our photographs, as well as our field observations, points to Slaty-backed Gull and rules out everything else.
All my observations were made using Zeiss 10x40 binoculars and a Kowa 60mm spotting scope (ED glass) with a 27x eyepiece, from a distance of 30 to 40 metres. Total observation time was about 20 to 25 minutes. The weather was cloudy with a few flurries. The temperature was about -11EC, and the wind was moderate out of the northeast. There was no snow cover. Lighting conditions were good.
One week later to the day, Glenn Coady and Patrick Stepien-Scanlon saw what they believed to be the same bird further to the east on the ice inside the breakwater, opposite the Boulevard Club. Their description fit the bird that I saw. Patrick also had a paler mantled Lesser Black-backed Gull nearby to compare with. Unfortunately the gull in question was on private property with no public access, and both observers had to content themselves with very distant and awkward views. They watched the gull fly out over the lake at dusk but neither was able to see much on it. It has not been reported since.
Bob Yukich, bob@kryukich.on.ca, March 5, 1999
since July 4, 2000 (Thanks WebCounter!)
