These following two paragraphs are from an article at "The Independent", and it is about the phenomenon called a murmuration;
Winter must must be coming... because the starlings are flocking. Here are many thousands of the birds wheeling together in the afternoon sky near Gretna Green yesterday, as they prepare to roost together for the night.Special thanks to Dinah Lord of Freerepublic for the link to the story on murmuration.
A starling flock like this is called a murmuration, a word that perfectly describes the rustle of thousands of pairs of wings. Starling murmurations are one of the most dazzling displays in the natural world, as the flock changes shape, one minute like a colossal wisp of smoke, the next a tornado, the next a thundercloud blocking the light.
The huge gatherings, biggest in winter, are boosted by thousands of birds that come to Britain's milder Atlantic climate to escape the harsh cold of the European continent, especially in Scandinavia. There are several reasons to get together in the way they do – safety in numbers, information exchange (if some come back from a good feeding area others may learn of it) and warmth at night through roosting together. The birds may feed up to 20 miles from their winter roost but return each evening.