Mystery Bird: Ross's X Snow Goose, Chen hybrid

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[Mystery bird] Ross’s X Snow Goose, Chen hybrid, photographed at Coronado Lakes, Santa Fe, New Mexico. [I will identify this bird for you tomorrow]
Image: Joseph Kennedy, 20 March 2008 [larger view].
Nikon D200, Kowa 883 telescope TSN-PZ camera eyepiece 1/1250s f/8.0 at 1000.0mm iso400.


Rick Wright, Managing Director of WINGS Birding Tours Worldwide, writes:
White waterfowl are an open trap for the unwary — in many parts of the US, at many times of the year, the most abundant such bird is Mallard, many of the cultivars of which are solid white, large, and chubby, leading continually to their being mistaken for something else. Domestic Graylags, too, are often white, and they, too, are often confused with native wildfowl.
No such danger with our quiz bird, which shows a head and bill shape utterly unlike that of a domestic Mallard or a white Graylag; this is a genuine white goose, which in North America narrows the field quickly to the two currently recognized members of the genus Chen.
The round head, short neck, large eye, rather steep forehead, and rather short, dark-colored bill with a bluish patch at the base are the standard marks for Ross’s Goose. Once the rarest of North America’s breeding geese, the population of this gentle little bird has increased in tandem with that of its larger cousin; and its range has widened, too, such that there is no longer anywhere in the US that Ross’s Goose can’t be looked for with reasonably expectation in the winter.
But there’s a problem, as there so often is. Snow and Ross’s Geese are closely related, and mixed pairs are not at all uncommon. It can be extremely difficult to distinguish between a “real” Ross’s Goose and a small, small-billed hybrid or intergrade. There are a couple of things about the individual in this photograph that bother me. The head — from this angle, at least — looks big, and not quite properly shaped for Ross’s Goose (or for Snow Goose, for that matter). The bill may be a bit long. The shape and extent of the dark patch at the base of the bill is odd, in my experience. And the bill appears to show a distinct blackish edge along the distinctly “open” tomia, creating a noticeable “grin patch” smaller than that on a Snow Goose but larger than that on a classic Ross’s Goose. If I saw this bird in the field, this well, I’d almost certainly call it a white Chen showing probable characters of hybridization.
Note well that I wouldn’t outright call it a hybrid. Maybe some of the geese that look like this are in fact “pure” Ross’s Geese, simply expressing some of the genetic potential of that long-ago Chen that was the ancestor to both Ross’s and Snow. And that possibility raises a series of philosophical questions that all lead straight back to the most important one of all: what do we mean by a species — and who cares? For the birder, or at least for me, it’s enough to have seen a bird that stretches what we think of as our knowledge in interesting ways. And this one certainly does that.
Review all mystery birds to date.

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About GrrlScientist

grrlscientist is the pseudonym of an evolutionary biologist and ornithologist who writes about evolution, ethology, and ecology, especially in birds. After earning a degree in microbiology (thesis focus: virology) and working at the Fred Hutchinson Cancer Research Center in Seattle, she earned her PhD in zoology from the University of Washington in Seattle, where she studied the molecular correlates of testosterone and behaviour in white-crowned sparrows. She then worked a Chapman Postdoctoral Fellow at the American Museum of Natural History in New York City, where she studied the speciation and distribution of lories and other parrots throughout the South Pacific Islands. A discarded scientist, she returned to her roots: writing. Formerly hosted by The Guardian (UK), she now writes about science for Forbes and for the non-profit think tank, the Evolution Institute and she writes podcasts for BirdNote Radio. An avid lifelong birder and aviculturist, she lives with a flock of songbirds and parrots somewhere in Germany.
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0 Responses to Mystery Bird: Ross's X Snow Goose, Chen hybrid

  1. RM says:

    Ross’s Goose

  2. JohnB says:

    A Ross’s Goose indeed.

  3. Rick Wright says:

    I’d be really interested in reading about HOW everyone identifies this bird.

  4. Bob O'H says:

    I guess the philosophers start with “it’s not black, so it can’t be a swan”.

  5. RM says:

    Rick,
    For me, I saw a goose that looked like a snow, but smaller. It has a shorter, more stubby bill, and the picture says it was taken in Texas which rules out the Atlantic and probably the Mississippi flyway. A Ross would definitely be found in the Central flyway in Texas.
    It just looked like a Ross when I first saw it. I chased waterfowl on couple different continents, hemispheres, and several countries before becoming a watcher only.

  6. bobk says:

    Short-round Whitegoose.
    I wonder what the latin for this name is.

  7. Selasphorus says:

    Ross’s Goose. Beak is too small and lacks a grin patch for it to be a Snow.

  8. Jerry Friedman says:

    Ross’s Goose, Leucochen brachycyclicus (for bobk). Same method as everyone else: it’s a small white goose with a short bill. (You could probably even get a definite measurement of the size if that’s Black Medic blooming in front of its right shoulder.) I must admit that the times I’ve identified Ross’s in the field, they’ve been standing next to Snow Geese.
    Santa Fe, Texas, not New Mexico (where I am), by the way.

  9. Bill says:

    Ross’s Goose. I’m comparing the head and bill shape with the examples in Sibley’s Guide to Birds, p. 79. The head of the goose in the photo seems less slender than any of the Snow Goose heads. The beak seems to have a straighter margin with the facial feathers than a Snow Goose, and the dark coloration in the nostril area seems more like that of a Ross’s Goose. The Ross’s and the Snow Goose are often found together which does make identifying the Ross’s easier; that’s how my wife and I first felt confident to add it to our life list. I don’t know enough about the current research about flyways, but there has been some challenges to that concept. The Black Swan is native to Australia, but I’m no philosopher – just a smart aleck.

  10. Rossi says:

    Ross’s Goose: the bill join is essentially vertical, there is no grinning patch, and the base of the bill is purpish.

  11. bobk says:

    With sincere deference to the master birders above, I’ve always found the bill to be of a muddy color.

  12. JohnB says:

    The only other bird it could be confused with is a Snow Goose, which has a larger, more uniformly colored beak and a noticeable black “grinning patch”. The base of the beak on Ross’s is warty and grayish or bluish.

  13. RM says:

    What features show that this is a cross?

  14. RM says:

    nevermind

  15. Jerry Friedman says:

    Thanks for the interesting id, Rick! I’ve asked people whether they think the little bird in this picture has some hybrid ancestry, but no one has considered anything but size. Would you do me a favor and let me know what you think? You can leave comments here or at the picture or e-mail them to me here.
    Thanks.

  16. Jerry Friedman says:

    Thanks for the interesting id, Rick! I’ve asked people whether they think the little bird in this picture has some hybrid ancestry, but no one has considered anything but size. I think the curved bill-head boundary and what I think is a “grin patch” indicate a hybrid even more strongly than features of the bird above. Would you do me a favor and let me know what you think? You can leave comments here or at the picture or e-mail them to me here.
    Thanks.