Yes, I have a childhood memory of swifts and ants standing in my parents garden. The houses and gardens were built on the top of a ridge so away below were fields and meadow. Suddenly an ants nest went 'critical' and out swarmed all these flying ants. The swifts were not waiting for them to gain height but fell out of the sky and swooped around me at high speed.
All the same the hunter becomes prey too, as there was a picture in the local paper recently of a hobby catching a swift!
http://www.oxfordmail.co.uk/search/4460213.Stunning_photos_show_bird_of_prey_in_action/