Brant (Branta bernicla), Bodega Harbor, 17 January 2013
This relatively small, dark goose overwinters in sheltered harbors and bays along the Pacific Coast where they feed on eelgrass (Zostera marina) and sea lettuce (Ulva spp.). They nest much farther north, mainly in Alaska and the Northwest Territories of Canada.
The white stripes on the neck are sometimes referred to as a collar or necklace. Interestingly, the amount of white in the necklace varies. I'm not sure if this holds true for Brant on the West Coast, but a study on Brant nesting near Hudson Bay found that geese tended to choose mates with similar necklaces!
Most of these geese were actively preening.
Some posturing was also evident. Note the raised and arched necks. I've read that Brant will defend both feeding and roosting sites.
Sometimes the posturing was fairly aggressive, with the neck being held low and horizontal and the bill open:
And occasionally there was a chase. The next picture also reveals the tail pattern. Note that Brant tail feathers are dark brown/black, but the uppertail coverts are very long and white, extending over the tail feathers and creating a bold white "V" pattern.
These handsome geese utter a distinctive call that is sometimes written as "rrronk." When the wind is still, their collective calls can be heard across Bodega Harbor. I don't have a great recording yet, but here's an example. You can hear some chattering first, and then a couple of rolling, guttural rrronks. I've repeated the recording once, so listen for the rrronks at ~4-5 seconds and again at ~10-11 seconds.