Breathtaking "murmurations" - dark, shifting shapes that look like vast dancing clouds - fill the skies of Israel in winter. First, a falling leaf, then a rising dove, now a giant whale swimming across the sky - migrating starlings from Russia and east Europe swoop and soar as they embark on their aerial displays in the evening. According to ornithologist Yossi Leshem of Tel Aviv University, the starlings do this to help one another find food and to fend off predators. A falcon or hawk will try to focus on a single bird, he said. By grouping together, not only do the starlings find safety in numbers but also their changing movements and shifting collective shape confuse would-be attackers. They can even create a sudden breeze with their synchronised movements, Professor Leshem said, causing a predator to fall flat on its back.