An impressive flight display by thousands of starlings who have come home to roost at the end of the day...

From the RSPB website:

It's basically a mass aerial stunt - thousands of birds all swooping and diving in unison. It's completely breathtaking to witness.
We think that starlings do it for many reasons. Grouping together offers safety in numbers – predators such as peregrine falcons find it hard to target one bird in the middle of a hypnotising flock of thousands.
They also gather to keep warm at night and to exchange information, such as good feeding areas.
They gather over their roosting site, and perform their wheeling stunts before they roost for the night.

https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/starling/starling-murmurations/