Cloud formations: Is it a bird? Is it a plane? No it's just a cirrus cloud that looks like an eagle Amazing cloud formation appears in Filton, Bristol Andrew Winter, 54, spots swallow-shaped cirrus cloud over industrial estate Apparition appears at time when real swallows are flying south for winter As summer ends and the air turns colder, the skies are filled with birds flying south for the winter - and this year they were joined by another winged creature of a more ethereal nature. But the eagle that appeared over Filton in Bristol this morning was not there to prey on the smaller swallows and swifts on their annual migration. Bird-lover Andrew Winter, 54, had taken a break from the office when he spotted the cloud formation that resembled a bird hovering over an industrial estate. Swooping: The wispy cirrus cloud that resembled a bird was photographed over Filton in Bristol this morning Mr Winter, 34, said: 'It was uncanny. I'd popped outside for a quick cigarette break and looked up and there it was. 'I ran back into the office and told everyone, but they didn't believe me. One joker asked me if I was cirrus - which of course I was. Cirrus clouds form at very high levels in the atmosphere - above 20,000ft. The extremely cold temperatures at these levels mean the clouds are made up of ice crystals, meaning they appear thin, wispy and white. Birds including swallows and swifts usually migrate from the UK in September and October, travelling thousands of miles to Africa, Arabia and the Indian sub-continent. They can travel more than 200 miles in a day at a maximum flight speed of 17-22mph. Icarus wings: The 'bird' appeared to be on a final descent like the figure from Greek legends who died when the wax holding together his home-made wings melted when he flew too close to the sun Flight of fancy: Andrew Winter rushed back to the office to tell his colleagues - many of whom did not believe him The bird-shaped cloud was just one of several amazing formations that have been spotted by keen photographers and cloud-spotters. Clouds shaped like continents have been seen in recent months, as have others looking like animals such as dolphins. Thanks to smartphones, more people are able to snap the beautiful images before they disappear. Meanwhile, flocks of birds are also known to form themselves into cloud-like formations. The annual murmuration of starlings in the skies over Scotland involves thousands of the birds taking to wing to perform a mating ritual. In the display that only occurs during winter months, the starlings use their amazing sense of spatial awareness to fly in a way that deflects predators. Flock: A murmuration of starlings over Gretna in the Scottish borders in November 2011 Continental drift: A cloud looking like the UK, left, spotted over Worcester in May 2009 and, right, a cloud that resembled Africa seen over Brockwell Park in London in July this year Sky dive: This cloud resembling a dolphin was snapped by two men driving a white van along the M11 in Essex in January this year