I was sitting on the balcony yesterday evening reading quietly when an alpine swift swooped past me, about one metre away. Swish. So I sat for a while and watched him and his mates enjoying their evening swoopageness, and it struck me after a few minutes that you don't hear or see the swifts in the morning. They don't begin to appear until after morning coffee; eventually by about an hour before sunset they have taken over the sky. They disappear again when darkness falls. I wonder where they go and what they're doing?
Meanwhile, at dusk the bats appear. They fly much lower than the swifts and their pattern of flight is quite different even though they too are catching insects. Being much lower in the air there's no thermals for them to glide on, I suppose. But they nevertheless avoid hitting the buildings.