Recently, a small group of birdwatchers spent three weeks around Mount Vernon. They were busy counting wild birds on Mount Vernon's wetlands, south of Washington, D.C. They began in the middle of December and worked until the beginning of January, 2015. The birdwatchers were among 70,000 volunteers who collected information for the National Audubon Society, a U.S. conservation group. They counted birds in more than 2,400 areas in the United States, Canada, the Caribbean Sea and other parts of the Americas. The Audubon Society's first "Christmas Bird Count" took place 115 years ago in 1900. At that time, a man named Frank Chapman suggested a new Christmas tradition that people count birds instead of shooting them around the holiday. Harry Glasgow has taken part in the Christmas Bird Count for the past 10 years. This year, he was one of the volunteer birdwatchers at Mount Vernon. "I think it's a tremendous use of a lot of unofficial talent around the nation to keep track of birds. Birds are one of the surest indicators of the health of ecology." Last year, the bird count recorded over 66 million birds of 2,403 different species. Gary Langham is chief scientist with the National Audubon Society. "The Audubon climate report says that half the birds in North America -- 314 out of 588 species -- are seriously threatened by climate change. The impacts sort of cut across all birds, all sizes, all kinds, all places." Information from the bird counts has shown that birds are staying farther north during the winter months because of warmer weather. Birdwatcher Jaime Reidy has noted the difference close to Washington, in the state of Virginia. "You get to see them at odd times of the year, a little earlier, staying a little later." Gary Langham says other conditions are affecting bird populations. "You can imagine the birds that live along the beach or along the rocky shore line as sea levels are rising around the world. That is impacting them, you know." David Yarnold is president of the Audubon Society. In his words, "Christmas Bird Count data is becoming important not only in documenting current climate change, but in predicting the future effects of climate change on North American bird populations. If we know what to expect, we can start taking actions now to do something about it." Which of the following is TRUE according to the passage?
Americans always have a habit of shooting birds during Christmas. Some birds needn't migrate to the south to survive the winter in the USA now. The volunteers of the National Audubon Society come from the United States, Canada. It's important to watch birds for they are the surest indicators of the health of the ecology.