Recently，asmallgroupofbirdwatchersspentthreeweeksaroundMountVernon．TheywerebusycountingwildbirdsonMountVernon'swetlands，southofWashington，D．C．TheybeganinthemiddleofDecemberandworkeduntilthebeginningofJanu

　　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 70，000volunteers who collected information for the National Audubon Society，a U．S．conservation group．They counted birds in more than 2，400areas in the United States，Canada，the Caribbean Sea and other parts of the Americas．

　　The Audubon Society's first"Christmas Bird Count"took place 115years 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 10years．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 66million birds of 2，403different species．

　　Gary Langham is chief scientist with the National Audubon Society．

　　"The Audubon climate report says that half the birds in North America-314out of 588species-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 atodd 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 shor