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.
The first Wilson's Warbler of the season was in the nets today. Their typical fall arrival date here on campus is 29 August, but the earliest date we've recorded them is 18 August. It's not too unlikely that they may arrive a little earlier, but we ordinarily don't do much field work on campus in July, so they could be overlooked. If you are interested in extreme and typical arrival dates for the common species in southeast Michigan, pick up a copy of my book, The Birds of Dearborn, An Annotated Checklist. You can have a PDF copy on our desktop in a few minutes for only $5!
The Wilson's was a young female. In a future post, I'll talk about how we age birds. As for determining gender, the nearly complete lack of a dark glossy cap is indicative of a female, as was the length of the wing. In many songbirds, males have longer wings than females. Although there is overlap in most species, extremes can indicate gender.
Another thing to notice in the photo above are her "whiskers" which are actually modified feathers known as "rictal bristles." Many birds have them, but they are most well-developed in species that forage for insects on the wing. The flattish bill shape and prominent (for a warbler) rictal bristles prompted Audubon to refer to this species as "Wilson's Flycatching Warbler."
At least, this bird had a tail. One thing we note for all Tennessee Warblers is the extent of the white spot on the outer tail feather. Not all of them have a spot; this one was quite large. It's not certain why there is such variation, but perhaps once we get a large enough sample size, we can see if there is any correlation with age, sex, or some aspect of geographic range.
I'll be back at the nets on Monday!
