We have been so lucky to have a huge flock of barn swallows visiting the pastures every evening.  It is so pleasant to watch them swoop and glide through the paddocks eating hundreds of mosquitos, gnats, etc.  They gather on the roof line, and almost like synchronized swimmers, they dive off and go about their business vacuuming the bugs from the air.  In about an hour, they are done and fly off; only to reappear like clockwork the next evening.