Walking last week in the eastern section of the cemetery, the sound of a sand martin made me look up.
I spotted, after a while, a large number of insects flying ponderously up from the grass. The swifts and martins were feeding. And looking at the grass I saw many brown beetles, garden chafers I believe, emerging, struggling in the thatch of the grass, and then taking to the air. Then the sun was covered by a cloud, and the beetles stopped emerging and the birds rapidly vanished.