在线英语听力室_免费在线英语听力学习网站

This is Scientific American — 60-Second Science. I'm Annie Sneed.

这里是科学美国人——60秒科学。我是安妮·斯尼德。

Every spring, a bird called the barnacle goose migrates from the coast of the North Sea to the Russian Arctic, where it breeds. That's a 3000-kilometer trip. Along the way, the geese usually take pit stops to rest and refuel. But the Arctic spring has been arriving earlier and earlier.

每年春天，一种名为白颊黑雁的鸟会从北海海岸迁徙至俄罗斯北极地区繁衍。这一旅程长达3000公里。白颊黑雁通常会在迁徙途中停下来休息并补充体力。但北极春天到来的越来越早。

So researchers analyzed¹ six years of barnacle goose migratory² tracking data. To try to figure out if these geese—and other species like it—can adapt their migration³, to stay in sync with the changing seasons.

因此，研究人员对白颊黑雁六年来的迁徙追踪数据进行了分析。目的是试图弄清这些黑雁以及其它类似物种是否能适应迁徙，与变化的季节保持一致。

"Then we used satellite images to see when snow was melting in the Arctic, and then we could relate the timing⁴ of the birds to the snow melt." Bart Nolet, an ecologist at the University of Amsterdam.

“然后我们用卫星图像来观察北极的融雪时间，接下来就可以将白颊黑雁的迁徙时间与融雪时间关联起来。”阿姆斯特丹大学的生态学家巴特·诺莱特说到。

Nolet and his colleagues found that the geese did not leave their wintering grounds sooner to match the earlier Arctic spring. But they did speed up their trip—by skipping many of their usual stopovers. The birds arrived in the Arctic up to 13 days earlier than they used to. But at a cost.

诺莱特和同事发现，白颊黑雁并没有提前离开过冬地以适应北极的早春。但是它们确实缩短了迁徙时间，跳过了许多通常会停留的休息地。白颊黑雁到达北极地区的时间比以前提前了13天。不过这是有代价的。

"So in a normal year, they start laying their eggs right after arrival. But now they spent more than a week foraging⁵ before they laid their eggs... So in effect, they weren't that much earlier than would have been the case, if they would be able to lay their eggs immediately. As a result, the chicks that hatch from the eggs in that early year, they survive much less than normal. Probably because they missed the food peak, which is a combination of very high quality in the grass, and enough grass around. And that food peak is around three weeks after snow melt, but now they were a few weeks later."

“在正常年份，它们一到达北极就开始产卵。但是现在，它们要先进行一周多的觅食然后再产卵。实际上，与之前到达后马上产卵相比，它们现在的产卵时间不会早太多。结果，在早春年份孵化出的小雁，存活率远低于正常年份。这可能是因为它们错过了食物高峰期，即周围草地质量超高且充足的时间。食物高峰期大约在融雪后的三周内，但是现在已经是几周之后了。”

With devastating⁶ effects.

这带来了毁灭性的影响。

"We looked at the daily survival of the goslings... If you calculate it over the whole month, then it's quite dramatic, they decrease from 20 percent to only 2 percent surviving. It basically means that not many goslings are surviving in such a year." The study is in the journal Current Biology.

“我们观察了小雁的每日存活率。如果一整个月都进行统计的话，那结果相当惊人，存活率从20%下降至仅剩2%。这基本上意味着在这样的年份里，没有多少小雁存活下来。”这项研究发表在《当代生物学》期刊上。

So why don't the geese just leave their wintering grounds earlier?

那为什么这些雁不能早点离开过冬地呢？

"When it's an early spring in the Arctic, it's not necessarily an early spring in the wintering area. So the birds cannot use any cue that's related to what's early or late spring to leave."

“北极是早春，但过冬地并不一定也是早春。因此，这些鸟无法利用早春或晚春的线索以决定离开时间。”

But Nolet does think there's some hope they might be able to adapt. "We know that the goslings learn their migration from their parents, so there's a lot of learned behavior in it. So it may well be that in the course of time, some birds discover that they have to depart earlier from their wintering areas to be able to time their migration perfectly⁷, and match it with the Arctic."

但诺莱特确实认为，它们有望适应这种现象。“我们知道小雁从父母那里学习迁徙，这其中包括很多习得行为。因此，随着时间的推移，一些鸟儿很可能会发现，它们不得不提前离开过冬地，以便能够完美地安排迁徙时间，并适应北极的早春。”

Thanks for listening for Scientific American — 60-Second Science. I'm Annie Sneed.

谢谢大家收听科学美国人——60秒科学。我是安妮·斯尼德。