Thursday, December 15, 2005

Small Canada Geese

In 2004, the 45th Supplement to the American Ornithologists’ Union Check-list of North American Birds split Canada Goose into two separate species: the larger forms remain Canada Goose (Branta canadensis) while most of the smaller forms are now Cackling Goose (Branta hutchinsii).  The Cackling Goose form most likely to be seen in Michigan is the former Canada Goose race B. c. hutchinsii, or Richardson’s Goose. The other small former Canada Geese are western birds that would be considered very rare in the east.  An excellent report on this is on the Ontario Field Ornithologists’ web site.  David Sibley’s website also provides great information.  In particular, read the information on neck size and voice, which from his discussion appear not to be as conclusive as some have been implying. There’s also a nice map indicating which races breed where.  The Ocean Wanderers web page, by Angus Wilson, includes photos, links to specific individuals being debated, and extensive literature citations.

What follows is some information on the identification of Canada Geese found in Dearborn, focusing on an interesting case of a “runt” Canada Goose from Canada.

The most common subspecies of Canada Goose in Dearborn is the Giant Canada Goose, or B.c. maxima.  This largest of the races was extinct in much of eastern North America, and in Michigan, at the turn of the 20th century, wiped out by hunting and habitat destruction.  Aggressive reintroduction campaigns resulted in the surplus of these big, non-migratory geese we see today.  This is the subspecies that nests in Dearborn.

During spring and (especially) fall migration, Giants are joined by the slightly smaller, somewhat darker-breasted migrant race B.c. interior.  Around the UM-Dearborn campus, many geese wearing orange neck collars can be found in the fall.  These birds have been banded on Akimiski Island, Nunavut, in James Bay (while closest to Ontario, all islands in James Bay belong to Nunavut, formerly Northwest Territories).  One neck-collared goose was seen by us in the fall of 1995 and again in the fall of 1998.  It was originally banded in 1990 on Akimiski.

There are other even smaller races of Canada Goose than  B.c. interior. An example is this goose, photographed by Jim Fowler, Jr. at Greenfield Village on 25 Oct 93.  Notice the pale breast, and small size compared to the nearby Giants.  This was probably B.c. hutchinsii (a.k.a. “Richardson’s Goose”), the smallest of the pale-breasted races.  They nest in the northern portion of Hudson Bay.

Next, look at this little dingy-breasted goose below, shown in these two pictures with one of  her two B.c. interior buddies that she hung around with from late September until early October 1998 on the UM-Dearborn campus.  This goose had a regular leg band and a colored leg band.  As it turns out, she was banded as a young female not yet able to fly on 15 Jul 98 on…Akimiski Island!  Since none of the small, dark-breasted races are known to nest in this part of Canada, I contacted the person who bands on Akimiski, Jim Leafloor of the Ontario Ministry of Natural Resources, for more information.

Dr. Leafloor explained to me that all the geese breeding on the island are considered B.c. interior.  This goose was banded on the north shore of the island, where the geese are smaller than other interiors due to low food availability.  The habitat has been degraded over the last two decades by high densities of nesting Canadas (seven times higher than on the nearby mainland and up to 300 times higher on the north coast of the island), use by migrant Brants (another type of goose), and especially increasing numbers of migrant and nesting Snow Geese.  Eggs of these birds when raised in captivity grow to “normal” size like their mainland counterparts.  Therefore, one should use caution assigning subspecies to varying sizes of Canada Goose seen in this region.

For more information on this very interesting phenomena, please see a paper Leafloor and his colleagues  published in the  journal The Auk:

Leafloor, J.O., C.D. Ankey, and D.H. Rusch.  1998. Environmental effects on body size of Canada Geese. Auk 115:26-33.

UPDATE: David Sibley has a post and photos on his site regarding recent research and evidence of hybridization between small (Cackling) Geese and larger Canada Geese. Please see Cackling-ish Geese; here is the paper he refers to:

Leafloor, J.O., J.A. Moore and K.T. Scribner. 2013. A hybrid zone between Canada Geese (Branta canadensis) and Cackling Geese (B. hutchinsii). Auk 130: 487-500.

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