Starling Murmuration - Isleham

Having heard yesterday about Starlings gathering at Isleham Marina at dusk, I checked them out this afternoon.   There were several hundred birds in small groups initially and reportedly about 20,000 in one huge murmuration by the end!   What an amazing sight!   Why do they swirl around making amazing patterns for about 30 minutes before suddenly dropping for the night into a reed bed?    Do they all leave at the same time in the morning when dawn breaks?   Something to investigate..........   In the second photograph is a falcon which was as mesmerised by the numbers as we were by the spectacle.