Cackling Goose (Branta hutchinsii hutchinsii) 11/24/06 Britton Ford Unit of the TNWR; Henry Co. Michael Todd

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1 Cackling Goose (Branta hutchinsii hutchinsii) 11/24/06 Britton Ford Unit of the TNWR; Henry Co. Michael Todd Cackling Goose, recently split from Canada Goose (AOU 45 th Supplement), is a regular visitor to TN; most often it seems in west TN. I have seen these birds numerous times, both before and after the split. All of my experience has been with birds that appeared to be of the nominate race, commonly referred to as Richardson s Goose. Jeff Wilson has photographed a bird or two that appear to possibly be of one of the west coast races, but by far the expected race of this species in TN is Branta h. hutchinsii. This report concerns 6 individuals of this species that I saw on the afternoon of 11/24/06, at Britton Ford in Henry Co. This has been a regular location for small numbers of these geese, as it draws comparatively large numbers of Canada Geese for the area. The max I ve had in TN is 44, also at Britton Ford, on 1/6/06. Numbers in the single digits are much more common though. And, Britton Ford also regularly hosts some small examples of Canada Geese. There was a lot of confusion initially regarding separation of Cackling/Canada, and in particular the hutchinsii subspecies from the smaller forms of Canada, such as parvipes (lesser) and small individuals of the interior race of Canada. While size is obviously one of the 1 st indicators of a possible Cackling Goose, the primary indicators at this time seem to be the shape of the head along with bill size/shape. Another secondary indicator is the length and bulk of the neck. It seems safe to say that most of the smaller Canada Geese we see in TN are interiors, though parvipes could possibly figure in the equation, though it should occur primarily to our west. Hopefully this part of the puzzle will be unraveled a little more over time. Irregardless, the same set of features can be used to separate hutchinsii Cackling Goose from small Canada Geese. I am attaching 3 photos from 11/24/06, with this report. Due to the distance involved, yards at the closest, the photos are a little fuzzy, but I still think show the look of the birds pretty well. I photographed these birds with a Nikon 4500 Coolpix through a Pentax PF-80 ED spotting scope. I watched these birds for minutes before they swam out of sight. The 1 st photo shows the 6 birds swimming alone, and shows the following primary indicators for Branta h. hutchinii: Very short, stubby bill obvious on all birds. The bill is less than half the depth of the head. In Canada races, including the small birds, the bill is 70% or more of the depth of the head. The shape of the bill also differs, with hutchinsii having an even culmen, and more steep angle from the base to tip, so without the thinner look of the Canada forms which narrow towards the tip, as the bill is typically concave. It has been shown that in at least some of the runt interior Canada Geese, that while the body never develops to normal size, the bill does. This gives these small Canada Geese a bill that can look larger in relation than that of the larger geese. The 2 nd bird from the left in particular shows the classic hutchinsii head shape. The forehead rises steeply from the bill then rounds off to a flat crown. The rear peak of the crown drops off very steeply to the nape, giving the head a very square look. This difference in head shapes is quite distinct from any of the Canada Goose races, including the smallest, parvipes. They lack the steep forehead line and squared-off head. It should be noted that

2 not all hutchinsii have as distinctive a head profile, apparently probably related to sex, but the classic look isn t shown by any of the other races of Cackling, or Canada Geese; these exhibit either a rounded or wedge-shaped head. The necks are short and thick on all birds, with the black sock being about as wide at the breast as it long to the chin. This feature is variable in Canada Goose of course, but these birds all look to be alert, and the 2 nd from the left in particular looks to have its neck extended, as the breast is pulled-up high out of the water. The 2 nd photo is similar, and has a female Gadwall close for comparison, illustrating that they are obviously pretty small geese. The same features are again visible, with the distinctive head shape being most apparent on the 2 left-most birds. The left-hand bird appears to have its next outstretched, as the breast is pulled-up very high, but the black sock is still as wide as it is long. The 3 rd photo has 5 of them trailing 3 Canada Geese. The difference in size is apparent, as is the relative length of the necks. This photo isn t very clear, but the small bills of the Cackling Geese basically blend in with the photo, while they are still distinct on the Canada Geese. It should be noted that these weren t especially large Canada Geese, what I would consider basically average-size interior Canada Geese; certainly not large examples of Giant (maxima) Canada Geese. I believe that the head and bill shape that is visible in the photos eliminates these birds being small Canada Geese, either parvipes or runt interior, as these retain the overall head and bill shape of the larger birds. This report was done from both notes and from my posting on TN-Birds. Though this species isn t currently on the state list, this is primarily because of the recentness of the split, along with identification difficulty. This last factor should continue to be refined as more people are really looking at all of these birds now. Some sources of info I referenced include: Identification of Cackling and Canada Geese in Iowa Cackling Goose -- Canada Goose Subspecies Identification Indicators Canada and Cackling Goose Subspecies The Sibley Guide is also a good reference for this ID issue. Mike Todd 178 Diamond Drive McKenzie, TN Birder1@bellsouth.net 2/18/07

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