Trumpeter Swans, yellow bill spots, and leucism

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Trumpeter Swan with yellow patches on the bill, a well-known individual in Scarborough, Ontario. This photo taken in Jan 2012 by Jill Ramsay, used by permission.

In a previous post I’ve talked about Trumpeter Swans with yellow bill spots as a source of  confusion with Tundra Swan. I speculated that the yellow spots might be showing because the birds are leucistic (lacking melanin). The responses to that post are worthy of a follow-up. Harry Lumsden, who has studied the reintroduced Trumpeter Swans of Ontario and knows them as individuals, says that yellow bill spots are rare but are shown by a small percentage of Ontario Trumpeters.

Leucistic swans do exist (Harry currently knows of three in Ontario) and can be recognized throughout their life by their pale yellowish legs. They show yellow and red patches on their bills until age two, some show yellow spots until age four, but otherwise their bills are all black like normal Trumpeters. Most of the swans showing yellow bill spots (like bird C24 shown in the photos here) have dark legs and are not leucistic.

Another interesting point is that this swan shows a rounded border of feathering on the forehead. This is typical of Tundra Swan, most Trumpeters have a more pointed extension of white feathers on the forehead. Harry Lumsden says this is another rare variation shown by some Ontario Trumpeter Swans.

Given the yellow bill spots and the rounded forehead feathering, it’s no wonder birders have been confused by this individual. We might even start to consider the possibility of a hybrid, but Harry has watched this individual swan from hatching, he knows its parents and grandparents, and there is no question that it is a pure Trumpeter Swan. It’s a good lesson in variation and the fallibility of field marks.

Trumpeter Swan showing unusually rounded border of feathering on the forehead. Same bird as above, photo taken in Jan 2012 by Jill Ramsay, used by permission.

4 thoughts on “Trumpeter Swans, yellow bill spots, and leucism”

  1. Of our last year’s brood of seven trumpeter cygnets at Bluffers Park, four are showing yellow lores to varying degrees. Interestingly their mother 083 carries the leucistic gene (she has a leucistic sister, H11). I will send a photo.

  2. I have seen and photographed one of these trumpeters with yellow lore in Toronto at Bluffers park. I have two good photos of this swan if there is a way of posting them. It was suggested by Mike Burrell that I contact this website.
    In the past I have seen C24 and reported it as a tundra swan

  3. I photographed what used to be Trumpeter Swan C24 on Nov 25, 2013 at Bluffers Park in Scarborough. It no longer has any wing tags. The yellow area is larger and brighter now, and it is a more solid yellow patch. I have close up shots of the piece missing from the bill. While I was watching this bird, I noticed that it didn’t look at all like a Tundra Swan. It was the same size as the Trumpeters, it carried its neck the same way, it was not whiter. The feathering on the forehead did cut somewhat quickly across the top of the bill without coming to a point, but other than that, it certainly looked like a Trumpeter. I have one shot showing a thick leg that is solid black. I would normally have seen the yellow patch, and immediately called the bird a Tundra, but having watched it for a good long while, I decided to search for info on hybrids, at which point I came across this blog.

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