Friday, February 18, 2011

Greg's white-cheeked goose rant... I mean, primer

Can you tell the difference? A pair of long-necked Canada geese with their chicks among short-necked Cackling geese. The Cackling geese are just getting started on their migration to the Arctic to breed, while these Canada geese have already had success locally! Fernhill Wetlands, Forest Grove, Oregon on 22 April 2006 by Greg Gillson.

 

Empidonax flycatchers, small sandpipers, immature gulls, female hummingbirds,... All these are notoriously difficult to identify. However, there is another abundant taxon that is proving to be surprisingly difficult for many birders to identify accurately on a day-to-day basis.

In 2004 the American Ornithologists' Union split Canada Goose into two species, creating the name Cackling Goose (Branta hutchinsii) for the smaller forms and keeping Canada Goose (Branta canadensis) for the larger forms.

As a reviewer for eBird, it seems that most birders still do not know how to separate them. What I see happening is that a birder will identify a few Cackling geese, and then lump all other geese they see that day into the catch-all "Canada Goose."

As you can see from the above photo, the larger resident Western Canada Goose is 45 inches long, while the smaller migrant Ridgway's Cackling Goose is only 25 inches long--barely larger than a Mallard. The Cackling Goose is named for its high-pitched yelping calls. The Canada Goose gives the stereotypical deep honking call.

I don't want to over-simplify (because this is a very complicated situation) but 80% of the time it is pretty much that easy. Big or little.

Yes, it is true that there are at least 3 races of Cackling and 4 races of Canada Goose in western Oregon. Yes, the largest Cackling (Taverner's) is very similar to the smallest Canada (Lesser). But, frankly, if you don't spend time with a spotting scope carefully analyzing these intermediate birds, then the proper label for eBird (and your personal list) is "Cackling/Canada Goose."



There is nothing wrong with listing 25 Cackling Goose, 50 Canada Goose, and 600 Cackling/Canada Goose on your list. In fact, such honesty and accuracy is praiseworthy.

In western Oregon it is unusual to see more than a couple hundred Canada geese at one location. Most of these will be the big resident honkers, the white-breasted Western Canada Goose. At the Willamette Valley goose refuges you may see 1000 of the dark-breasted Dusky Canada Goose, but the entire world population of this form is perhaps only 7000 individuals. There may be a few Lesser Canada Geese mixed in.

The tiny, dark-breasted Ridgway's Cackling Goose is an abundant migrant and common winter visitor in western Oregon. Taverner's Cackling Goose is common in winter.

As an eBird reviewer for northwestern Oregon, I expect to see perhaps 100 Canada Goose and 5000 Cackling Goose on your non-summer lists, as typical. At Finley NWR, near Corvallis, Oregon, maybe 1000 Canada Goose and 7000 Cackling. Do you see that, in general, I expect 7-50 times as many Cackling geese as Canada geese? How does that compare with what you are reporting?

 

Cackling GooseDo you recognize that these are Cackling geese, and not Canada geese? Forest Grove, Oregon, 10 October 2009 by Greg Gillson.

 

East of the Cascades, in the Great Basin, I expect more Western and Lesser Canada geese and fewer Cackling. But I am uncertain of the exact ratios and seasonality there. But don't expect eBird to help, as the reports of these two species is all mixed up. And reports before 2005 will all be Canada Goose.

The big challenge is Taverner's Cackling Goose and Lesser Canada Goose. I think that Sauvie Island, Oregon and Ridgefield refuge, Washington, are probably the locations where these similar forms are most equally-common. Perhaps also Klamath Falls area. If anyone of you knows, please leave a comment.

Here are the scientific names of the white-cheeked goose forms mentioned in this post. These are the most-likely forms to be found in the Pacific NW. They are listed generally from largest to smallest:
Western Canada Goose (Branta canadensis moffitti)
Dusky Canada Goose (Branta canadensis occidentalis)
Lesser Canada Goose (Branta canadensis parvipes)
Taverner's Cackling Goose (Branta hutchinsii taverneri)
Ridgway's Cackling Goose (Branta hutchinsii minima)

 

Cackling GooseCackling geese have short necks, the dark breast indicates these are the abundant Ridgway's form, Forest Grove, Oregon, 17 October 2008 by Greg Gillson.

 

Largest and smallest, and both most-likely of all the forms: Western Canada Goose facing left, Ridgway's Cackling Goose facing right. Notice how the wing tips extend far past the tail on the Cackling Goose, but the wings are shorter on the Canada Goose. Hillsboro, Oregon, 31 December 2010 by Greg Gillson.

 

Ridgway's Cackling Goose are barely larger than Mallards. The rightmost goose is slightly larger with more sloping forehead and longer bill and paler breast and may be Taverner's Cackling Goose, Hillsboro, Oregon, 31 December 2010 by Greg Gillson.

 

I hate not being able to put a name on a bird. But, frankly, I still don't know whether this flock of 300 geese are Taverner's Cackling Geese or Lesser Canada Geese (or something else, or both). They go down on my list as "Cackling/Canada Goose" or "white-cheeked goose (species)" or "Canada-type Goose," but not "Canada Goose." The small out-of-focus goose in the back with purplish-brown breast facing left is Ridgway's Cackling Goose, Hillsboro, Oregon, 31 December 2010 by Greg Gillson.

 

If you are interested in pursuing this more thoroughly, you may start with Harry Kruger's page.

We've discussed these geese previously in At the pond... Canada Goose and At the pond... Cackling Goose

3 comments:

  1. Great photos pointing out these differences. Thanks!

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  2. Thanks for this post. It's just what I needed. About a month ago I saw a smaller goose, came home & looked it up on ebird. I decided it must have been a cackling goose. But, I was still slightly unsure. Thanks to this post, I'm almost positive it was a cackling goose.

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