Visitors gather to watch black-headed gulls at the Caohai Dam at Dian Lake in Southeast China’s Yunnan province. As spring approaches, the weather is warming up, and the black-headed gull is about to fly back to Siberia, where they breed. It is said that the earliest the black-headed gull usually reaches Kunming is mid-October, and the rest will arrive by mid-November. When spring comes the next year, the white feathers on young black-headed gulls will turn black, which means the bird has reached sexual maturity. Then it's time to begin to head north to breed.These days, many Kunming citizens and visitors have come to Haigen Dam at Dian Lake to enjoy seeing the birds before they depart.[Photo/Xinhua]