Every autumn, hundreds of polar bears descend on the small Canadian town of Churchill. Diana Preston watches them as they prepare for their annual migration north.
A baby polar bear with its mother on the shore of Hudson Bay, Manitoba
A tundra-buggy transports visitors on the lookout for polar bears across the icy landscape
Young males spar to keep their muscles toned as they wait for the hunting season to begin
A polar bear relaxes in the sun on the shore of Hudson Bay
