Bird migration

I spent a couple of hours on the patio, watching the constant movement south of several species of bird. In the time I counted (2 hours) I recorded, 4 house martins, 4 swifts, 207 swallows, 27 lesser black backed gulls and 1 black headed gull. Also seen were 2 resident common buzzards. A humming bird hawkmoth was also seen, feeding at dusk on the garden buddliea