Tern up for the books

Having just mis-identified a Common Tern what do you need but the quandry of having a Marsh Tern flying its pattern in front of you knowing that you may call good people to the site to see what may be a juvenile Common Tern. Such was the problem as I headed up to Hexham for the Planning Committee meeting, stopping off at Whittle Dene on the way. A Tern on the western Reservoir sitting on a buoy looked interesting but the wind was blowing and with the bird facing away the scoped views didn't conclude much.

Then it took off and flew, laying down what could almost be an invisible line on the water over which it flew from one end to tother, diving, darting never touching the water but picking off insects as it went to get to the end of the line to return and repeat the process. My vast knowledge of this species (three previous encounters) concluded marsh tern but which one?

I pondered and consulted the Collins Bird Bible. Initially the rump appeared white but upon closer inspection may be grey. Then a shot from the side showing the dark band on the chest near wing. Well, that's it then, Black Tern and I bottled it posting a possible ( I later discovered somebody else had fortunately reported earlier confirming Black Tern juvenile) A car pulled up and a birder I recognised but whose name escapes me scanned the adjacent field of Common / Black headed Gulls. I identified the bird to him and he noted it, and possibly another had been present on the lower reservoir for some time but had not been reported as there is no public access to that area.

As I left for my meeting the sun came out and I swore but another year tick was recorded. I wonder how many Tern puns there are?