.Canada geese are also quite a bit larger which is easy to see if you see the birds together. Imagine a herring gull and a Canada goose standing next to each other and what the medium size bird between them might be and you will have an idea about the size of a brant.
Here you can see them in relation to the gulls around them.
Brant don't nest here but are arctic nesters, like many of our winter visitors. They come here because our coastal waters often stay open and their favorite foods are plentiful They will eat seaweeds, especially sea lettuce if their favored eel grass is in short supply. Back in the 1930s when eel grass crashed the brant population crashed along with it but they have steadily been increasing in numbers and are once again flourishing.
And if you are an old school birder, yes, brant used to be spelled brandt ;-)