Breathtaking "murmurations" - dark, shifting shapes that look like vast dancing clouds - fill the skies of southern Israel and surrounding areas in winter.Starlings from Russia and east Europe winter in the Holy Land, swooping, pivoting and soaring, putting on a display to shame any aerobatics team anywhere.A Reuters video shows a remarkable display of shapes. Now they are a falling leaf, now a rising dove, now a giant whale swimming across the sky.They embark on their spectacular aerobatics in the evening. They do it, according to ornithologist Yossi Leshem of Tel Aviv University, both to help each other find food and to fend off predators.A falcon or hawk will try to focus on a single bird, Leshem said. By grouping together, the starlings not only find safety in numbers but their changing movements and shifting collective shape confuses their would-be attackers.They can even create a sudden breeze with their synchronized movements, he said, causing a hawk or falcon to fall flat on its back, not unlike an aircraft hitting windshear.Until 20 years ago, starlings came to Israel in their millions, usually descending on the northern part of the Negev desert, which remains warm in winter. But for unknown reasons their numbers have dropped. In the past few years they have come in flocks of no more than a few hundred thousand.Avid bird watchers and families gather over the weekends to spot the dazzling displays, with the birds twisting and turning at high speed, creating dramatic, sweeping patterns in the sky, contracting and expanding like a spiralling tornado.They can be seen in Israel above a rubbish dump near the southern Israeli city of Beersheba, where they feed during the day and circulate on warm air rising from the detritus.At dusk they begin to group together for the night. Some make off to streams near the Israeli town of Netivot, near Bedouin villages and an industrial park.