The towpath on the eastern side of the Exeter Ship Canal just to the north of the swing bridges can occasionally be hazardous in the spring if any of the numerous swans decide to build their nest on the canal bank; woe betide anybody - cyclist or pedestrian - who gets too close to any cygnets.
This happens on the Grand Western too. Closer to Tiverton, the swans are generally fairly tolerant. The closer you get to Holcombe Rogus, the friendlier they aren't. Happily, the same is not true of the people.