On behalf of Peter who sent in an email:-
I was out near the River Rye Malton watching Sand Martins in their usual place.. Two pairs of other birds I have never seen before, flying very close to the water playing catching insects
Small birds distinctive black and white stripe plumage on the dorsal surface Very agile. Wings so fast they looked blue at times.. These birds were acting almost like dragon flies. I watch birds often at this location on the bridge.
Sand Martins nest in the mud bank between March and late August but I have never seen these birds before. Not in the last 16 years.