Tuesday, January 10, 2017

A Special Guest Appearance at CSU Stanislaus: Cackling Geese!

Flocks of Canada Geese (Branta canadensis) are a commonplace sight around urban ponds in the Central Valley.  Ponds on the campus of California State University Stanislaus boast a substantial population of the large waterfowl year-round, augmented by overwintering birds this time of year.  While out for a walk a couple of days ago, I noticed something small and out of place as we passed a flock of Canada Geese: one of these geese was not like the others!  One of these geese was significantly smaller than the others; one was a Cackling Goose (Branta hutchinsii)!

Notice the small size of the Cackling Goose on the left, compared with much larger Canada Geese.

I'm sure most people would have walked right by (perhaps even with some level of annoyance at the mess the geese leave behind and their habit of blocking traffic).  But not I!  I excitedly returned with my camera and discovered there was not just one, but four Cackling Geese at the pond!

Note the short bill of the Cackling Goose, and the hint of a white neck ring.  The ring isn't as pronounced as is typically
seen in the Aleutian subspecies, but maybe this could be a variation or a hybrid between subspecies?

You might still be wondering what all the fuss is about.  Like I said, we see geese all over the place.  But not these geese!

These geese, Cackling Geese, are a relatively new species, as of 2004.  Previously, they were considered to be the smallest subspecies of the Canada Goose.  (For more on "lumping," "splitting," and new species, read this post on the California Scrub Jay.)

Branta hutchinsii minima

Ornithologists have determined that Cackling Geese are distinct enough to be classified as their own species, with four subspecies, two of which find their way to our Great Central Valley during the winter.  The subspecies B. h. minima is the smallest of the four, with a dark brown to purplish cast on the breast.  The subspecies B. h. leucopareia, known as the Aleutian Cackling Goose, has a complete and prominent white neck ring; this subspecies has been considered endangered in the recent past, but has since been delisted. 

Cackling Geese breed in the Arctic, in coastal marshes and tundra ponds.  Their diet is entirely herbaceous, consisting of plants such as grasses, sedges, grains and berries.  They migrate south for the winter, spending the cold months in the central potion of the United States and the Great Central Valley.

Compare the size of these Cackling Geese to that of a Mallard.  They're pretty comparable, which is surprisingly
and obviously small for a goose.

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