I stood at the window. A grey, windy morning with little to see. Boating through a strong headwind, a herring-gull flotilla was making for a newly ploughed field on the far side of the parish. I was about to return to work when a lone gull caught my eye. A glance showed that this one was different. Not a gull. Whiter, sharper-winged, this sea bird was elegant even as it tacked its way into the near gale. Lightning-strike wing beats and a streaming fork tail – surely a tern. It flew over the house and was gone. Common or Arctic tern?