While watching the Elvers navigate the Burn I also noticed one Three-spined Stickleback, over the next few weeks I watched this one fish in the same little pool out of the main flow, this was the only fish spotted on this length of the burn. This possed a few questions, the 1st, how did the stickleback get in the burn, there is no loch from which the fish could come from, this is a drainage burn, I asked the question on Orkney Nature Facebook page, two answers were plausible, the 1st A young Child may have put it there, 2nd A bird may have brought a fish egg on its feet or feathers, the 1st answer is only remotely possible, there is no access to the burn except this one house and the last owner was a man of seventy who never married and lived there from the age of ten, the 2nd answer even more remote, I think I am right in saying the nearest body of water with fish in is on the next island as the crow flys around eight miles away, and then land in a burn under thirty inches wide. Google had the answer, Sticklebacks can live in salt water, so the fish may have come by sea.
The Burn exits twenty feet above the high tide mark. Elvers can travel out of water but not the Stickleback.