There were a group of 6 Cackling Geese in the flock of Canadas. The adults (labeled "a") were larger than the first year birds. Note the vertical foreheads, short (and in some birds) drooping bill.
David Sibley just put a post on his blog discussing aging of geese. First year birds have a duskier demarcation between the black of the neck and the brown of the breast. They also have smaller, more pointed feathers on the back leading to less pronounced barring of the upperparts. Here again are the 2 adults (the rear and trail birds) flanking 2 of the younger birds.
But there were other geese too. The rearmost bird here is a mystery. In the foreground is a blurry 'Giant' Canada. The middle 3 birds are 2 of the young Cacklers with an adult Cackling trailing behind. The rear-most bird shares the vertical forehead of the cacklers but is decidedly larger. It seemed to associated loosely with the cackling geese, more so than with the Canadas.
Here again is the medium sized goose, this time next to 2 of the migrant 'Interior' Canadas. Its the 2nd bird in line and while smaller than the Canadas, isn't dwarfed like it was by the resident 'Giant' Canada in the above pic.