It's a spectacular sight - thousands of starling birds flying together to create mesmerising patterns called 'murmurations'.
It's thought it could be a form of protection from predators, or a way of signposting a roost.
A big public survey is taking place to collect sightings of starling murmurations. It's hoped the data can be used to find out more about the birds' ballet moves.
A starling is a common garden bird, although numbers have fallen dramatically since the 1970s.
Starlings are slightly smaller than blackbirds and have speckles on their body.
The best time to see murmurations is between October and March.
They can be seen almost anywhere - including over big piers and also over wetlands and farmlands.
People are being encouraged to report any starling sightings by searching for the starling mumuration survey online and filling it in.