So this has been very helpful with recent work, locating exactly where birds are going, and trying to find out how they move from the winteringarea to the breeding area.
新的技术对科研工作帮助很大，科学家可以精确的判断鸟的方位，以及它们从越冬地飞往繁殖地的迁徙路径。
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But researchers say the only explanation for why so many birds over such a broad area are wintering in more-northern locales is global warming.