The chimney swift eats a large variety of insects and other invertebrates. Its diet includes the likes of ants, caddisflies, bees, wasps, and beetles. Some of the more unusual critters regularly consumed by what some folks call “flying cigars” are fleas, airborne spiders, termites, and even fire ants.
It has been estimated that a pair of chimney swifts feeding three nestlings captures the equivalent of 5000 to 6000 fly-sized invertebrates per day.
Between swifts and bats, I should ne well protected!