I think from time immemorial, the brant have used both sides of the James Bay coast. The information we do have going back, perhaps, to the 1930s or 1940s, or the kinds of anecdotal information available from then, suggests that the favoured areas were along the east coast of James Bay, where there are dense eelgrass beds. There is some eelgrass on the Ontario side, but we don't have good information on it; all we know is that it's far less abundant, or at least was far less abundant, on the Ontario coast. But there are other habitats.
Perhaps one of the big advantages of James Bay as a migratory stop-off area for geese is that there is a variety of habitats. Amongst the habitats available in James Bay, in addition to the eelgrass beds, is another habitat we call salt marsh meadows or salt marshes. There are patches of it along the Quebec coast, small pockets of it, and there are also huge pockets along the Ontario coast. The food the brant can get out of that habitat is the same food as they can get on their breeding grounds.
When they're on their breeding grounds, they are beyond the northern limit of eelgrass, so they don't have any access to eelgrass when they are breeding in the Canadian Arctic, but they do have access to the same plant that is growing on the upper levels of the tidal area near the eelgrass beds. So there is potentially an alternative source of food for them in these marshes. That could explain what we feel has occurred in the last decade or so, when the birds have tended to use the west side of James Bay more frequently than in the past, at the expense of using the Quebec coast of James Bay.