Good morning An intersting topic indeed, I doubt that what you saw hunting over the water was a Sparrow hawk. It is more likely to be a Hobby which is a falcon!(Falco subbuteo) and not a hawk they have different wing shapes. The staple diet of Hobbies is small birds which they usually catch on the wing as well as Dragon flies. They also take Swallows as they are one of the few fast and manouverable enough to catch them. I spent some time studying Hobbies as part of my degree last year. The word Falco comes from the latin for cicle shape or pointed wings hawks have rounded wings. Fox terrier