Springtime's arriving earlier across North America. But the degree of change isn't the same everywhere, which could spell trouble for migratory birds. Christopher Intagliata reports. 

北美的春天到来时间变早了，但是各地的变化程度不尽相同，这可能会给迁徙的鸟类带来麻烦。克里斯托弗·因塔利亚塔报道。

撰文播音：克里斯托弗·因塔利亚塔（Christopher Intagliata）

翻译：邱燕宁

审校：张清越

Climate change means springtime's arriving earlier across North America. But the season's onset isn't changing at the same rate across the nation.

气候变化意味着春天会更早到达北美。但在全国范围内，这个季节的开始时间并没有以同样的速度变化。

"Spring is not advancing as quickly in southern regions as it is in northern regions." Eric Waller, a biogeographer at the U.S. Geological Survey. 

“南方地区的春天没有北方地区来得快。”Eric Waller说，他是美国地质调查局的一位生物地理学家。

He and his team analyzed more than a hundred years of data on when the first leaves and flowers emerge across North America. And they found that although spring has sprung earlier nearly everywhere, in certain wildlife refuges, the season hits extremely early. 

他和他的团队分析了一百多年来有关北美第一批枝丫和花朵何时出现的数据。他们发现，尽管春天几乎在所有地方都来得越来越早了，但在某些野生动物保护区，这个季节来临提早得更加极端。

And that mismatch could be a problem for migratory birds, who might leave their temperate overwintering grounds down south at the usual time, only to find they've arrived up north too late. "Their food resources might be withering and they might not have as much food available to them. And that could affect their reproduction, their breeding."

这种不匹配可能对候鸟造成麻烦，它们或许会在正常的时间离开温带越冬地往南飞，却发现自己到达北方的时间太晚了。“它们的食物资源也可能正在枯竭，因此它们会没有足够的食物。这会影响它们的繁殖和育幼。”

The analysis is in the journal PLOS ONE. [Eric K. Waller et al., Differential changes in the onset of spring across US National Wildlife Refuges and North American migratory bird flyways] 

该分析发表在《PLOS ONE》杂志上。

The upshot: it may be more difficult than we thought to predict the effects of climate change on migratory birds. But the data might help land managers decide which plots of land to acquire, to augment existing reserves—and in doing so, ensure that even later birds still get the worm.

结果是:预测气候变化对候鸟的影响可能比我们想象的要困难得多。但是，这些数据可能会帮助土地管理者决定去获取哪块土地，来增加现有的保护区——以此确保即使来得较晚的鸟类也能获得食物蠕虫。