There has been considerable discussion about the gull that I found on Saturday in Ottawa. The matte grey plumage, contrasting white head, dark wing tips lacking mirrors, and all dark bill were interesting enough for me to put out an alert on the bird as a Heerman's. Fortunately several dozen people got out to see the bird, and some distant photos obtained; here is the best of them: http://www.facebook.com/photo.php?fbid=10150590161063133&set=a.10150590160953133.376498.663403132&type=1&theater The viewing conditions were poor, but most people were satisfied with the identification as a Heerman's Gull. Nonetheless, there were several features which bothered me about it. Most importantly, I was bothered by the fact that as far as I could see the bill was entirely black, not red based, except for a pale tip (nail). This might have been an artifact of lighting, red being the first colour to fade in low light, but the bills of nearby birds showed well. Secondly, while the bird was clearly darker than the Ring-billed Gulls it was associating with, it did not seem to be dark enough to be a typical Heerman's Gull. Thirdly, the configuration of the white on the head seemed wrong, and the demarkation between the white head and the grey underparts and nape, too sharply defined (almost like a dark hooded gull in reverse). So what is it? On balance I think the features just mentioned, make it unlikely to have been a Heerman's. I briefly flirted with the idea that it could be a Grey Gull, but here too there are problems; while Grey Gull has a black bill, the proportions are wrong as it has a conspicuously long, slender bill. So where does this leave us? A hybrid is one possibility, although it is hard to imagine what the pairing might have been (Heerman's x California?) Another possibility is a partially melanistic bird. Melanistic gulls are rare but occur. The photographs I have found show birds that are uniformly sooty, much darker than the Deschennes bird. Another possibility is a "grey washed" bird. Fortunately there are photographs of this aberrant plumage, for example this grey Ring-billed Gull photographed in the USA: http://home.comcast.net/~geoffrey.williamson/soiled_ribgul.html Even more interesting is this white headed, grey Black-legged Kittiwake in Quebec: https://picasaweb.google.com/lh/photo/ONzUL-TUHQxu0sbT8qqJ5w Other than the yellow bill and the proportions, the latter bird is virtually identical to the Ottawa gull. I now believe that the Ottawa gull was such a grey washed individual, probably, based on structure and probabilities, a Ring-billed Gull. This is not a plumage I was familiar with and appears to be very rare (cf it is not mentioned for Ring-billed Gull in Malling & Olson's "Gulls of Europe, Asia and North America"). The one feature that does not appear to fit this hypothesis is the dark bill, as, at least in the photographs I have found, the normal bill colour is retained. I would like to thank the many people who came out to see or look for the bird, and those who commented on my facebook posting and replied to my various e-mails. In particular I would like to thank Jean Dubois and Gary McNulty (Quebec) for sharing their thoughts, Bruce MacTavish (Newfoundland) and Alvaro Jaramello (California) for their insights, and Olivier Barden for his instructive picture of the Kittiwake. Mark GawnOttawa _______________________________________________ ONTBIRDS is presented by the Ontario Field Ornithologists - the provincial birding organization. Send bird reports to [email protected] For information about ONTBIRDS visit http://www.ofo.ca/
