Subject: Canada Goose Subspecies ID (long but informative)
Date: Oct 26 14:12:14 1995
From: "M. Smith" - whimbrel at u.washington.edu



In response to the earlier post regarding Cackling Canada Goose, here is a
little note I received from a friend who studied Aleutian CAGO on
differentiating subspecies. I know not the author, though they might be
Paul Springer and RB McNab. This should be of interest to most western
birders, as many subspecies pass through our region. The most common are
the Western CAGO (moffiti) which breed and winter here, and the cackling
CAGO (minima), which are common on the coastline in migration. Aleutians
(leucopareia) have been confirmed from Washington, though they are rare.
I have slides of a bird I believe is Aleutian on the UW campus two years
ago, though this cannot be confirmed, since there is a small amount of
overlap between minima and leucopareia. In the slides, it is feeding with
Western CAGOs, and an intermediate bird, perhaps a Lesser? The only real
way to know is by reading bands and tracing it back to the Aleutian
population (which is, BTW, federally listed). The account for Western
CAGO says they may have a red neck collar, though some of these birds on
the UW campus have white ones. And for all subspecies, the characters to
key in on are:

1. Relative size
2. Bill size/shape, and head shape/proportions
3. Presence and size of white neck ring
4. Whether or not the white cheek patches are continuous under the chin
or interrupted by feathers
5. Breast color
6. Presence of any neck collar or leg band is very useful

Any sightings of Aleutian CAGO should be documented, and details sent to:

Aleutian Canada Goose Investigation
c/o Wildlife Field Studies
Humboldt State University
Arcata, CA 95521
(707) 826-4759

Here's how to tell the subspecies apart in the field:

Cackling Canada Goose (Branta canadensis minima)
- Smallest CAGO, 1.5 times the size of a Mallard
- Relatively rapid wing beat
- Call is a high-pitched yelp
- Breast dark brown or bronze color, often with purplish cast
- Short, stubby bill, usually less than 1.25 inches long
- White neck ring sometimes present, but generally very thin and incomplete
- Forehead slopes back from bill, roundish head shape
- Cheek patches often continuous under head, but many separated by black
feathering
- Could have yellow plastic neck collar (so do some White-fronted Geese)

Aleutian Canda Goose (Branta canadensis leucopareia)
- Slightly larger than Cackler
- Breast color variable, but usually gray-brown, never with purplish cast
- Bill length usually 1.25-1.5 inches
- White neck ring present in *all adults*, usually wide and pronounced
(hatch-year birds generally don't exhibit good neck ring until first
spring)
- Thin dark border of feathering usually present just below white neck ring
- More abrupt forehead and flatter top to head than other small CAGOs
- Cheek patches nearly always separated by black feathering under chin
- Could have a light gray plastic neck collar or a colored leg band
(usually blue, yellow, red, or green).

Taverner's Canada Goose (Branta canadensis taverneri)
- Closely resembles Aleutian in many respects, but usually slightly larger
- Breast color variable, but usually slightly lighter than Aleutian. Darker
breast than Lesser (B. c. parvipes)
- Can have white neck ring on occasion, but almost always incomplete.
- Rounder head than Aleutian
- Usually has continuous white cheek patch under head, but not always

Lesser Canada Goose (Branta canadensis parvipes)
- Medium-sized goose, usually slightly larger than Taverner's
- Light breast color
- Overall shape and color resembles 'mini-Western'
- White cheek patch almost always continuous under head

Dusky Canada Goose (Branta canadensis occidentalis)
- Medium-sized goose, larger than Lesser, smaller than Western
- Dark breast color, typically a rich chocolaty brown, but may also
tend towards gray
- Neck seems to merge with chest, few birds show neck ring
- localized distribution in California, in northern coastal area

Western Canada Goose (Branta canadensis moffiti) aka Great Basin CAGO
- Largest CAGO in the West, twice the size of Aleutian
- Relatively slow wingbeat
- Call is a deep, resounding, 'ahh-onk'
- Light breast color
- Long bill and neck
- Could have red (orangish) plastic neck collar

-------------
Michael R. Smith
Univ. of Washington, Seattle
whimbrel at u.washington.edu
http://salmo.cqs.washington.edu/~wagap/mike.html