During autumn, dark clouds begin to form in the sky above fields, woodlands and reedbeds. But these are no ordinary clouds. They are one of the UK's most incredible wildlife spectacles.

Throughout the autumn and winter months, hundreds of thousands of starlings turn the sky black around the UK. The birds come together in huge clouds, wheeling, turning and swooping in unison.

Early evening, just before dusk, is the best time to see them across the UK as they perform their aerial dance and choose their communal night-time shelter. They roost in places that are sheltered from harsh weather and predators.

They tend to roost in woodlands, but reedbeds, cliffs, buildings and industrial structures are also used. During the day, however, they form daytime roosts at exposed places such as treetops, where the birds have good all-round visibility.

Autumn murmurations usually begin to form in November, though this varies from site to site and some can begin as early as September. More and more birds will flock together as the weeks go on, and the number of starlings in a roost can swell to around 100,000 in some places.

The huge gatherings are at their largest in winter, as they are boosted by thousands of migrant birds visiting from Europe for Britain's milder Atlantic climate.