Thursday, December 8, 2011

Ross's vs. Snow Goose

The day after Thanksgiving I photographed this white goose at Garr Ranch on Antelope Island in Utah. Everyone was already calling it a Ross's Goose, so I just went along with the identification and never even looked it up for any additional study. Then David Sibley yesterday posted pencil sketches of head shapes for Ross's, Snow, and possible hybrids, so I thought I'd do a little comparison and double check the identity of this goose.

So, in Photoshop Elements, I took my goose image, flipped it, took out all the color, and re-sized it to be proportional to David's sketch., Then I moved my goose head around over the sketch comparing it to each drawing looking for a match. I hope Mr. Sibley won't mind that I am borrowing his copyrighted sketch without even asking permission, but I really wanted to show how one can use the awesome identification and comparison tools he comes up with.
Looking at head-shape, my goose doesn't have the roundness shown in Sibley's sketches of the Ross's Geese. Mine has more of flattened head similar to the bottom Lesser Snow Goose drawing. The bill shape and relative bill size however really seem to be the identification clincher. My goose has almost no grin patch compared to the Snow Goose. The length of the bill is also proportional to that of a Ross's Goose. Sibley mentions in his post about the relatively flat lower mandible on a Ross's. My image does not show a lower mandible as flat as his sketches, but it's probably within a reasonable variance, plus my photo angle is not exactly the same as sketch-angle.

Anyway, I was safe trusting in the i.d. skills of my fellow Utah birders in calling this a Ross's Goose. Yet, going through an individual exercise of study and comparison sure has taught me a lot more and I think I'm just a bit of a better birder now.

Finally, one last photo of the Ross's Goose with an outstretched wing. This is for those intrepid birders who might want to use the wing feathers to try and age and sex this bird. I don't know how to do this myself, but I figure the whitish secondaries contrasting with the dark primaries might hold a clue. I also think that the white feather shafts on those dark primary feathers look pretty cool.


  1. Males = females by plumage. Looks like a hatch year bird due to the grayish wash to the face, neck and back.

  2. That's some gold ol' fashion police work there Robert.