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科学美国人60秒:气候变化导致脑类小鸟们数量表少

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Shahla Farzan: This is Scientific American’s 60-Second Science. I’m Shahla Farzan.
 
这里是《科学美国人》的 60 秒科学。我是莎拉·法赞。
 
Climate change is affecting animals in a lot of different ways. But scientists have noticed a common trend across a variety of species: they’re getting smaller. As in—physically smaller in size. But why, and what could this mean?
 
气候变化正以多种不同的方式影响着地球上的动物,但科学家注意到了一个存在于多个物种的普遍趋势:它们都在变小,物理意义上的体型变小。但这是为什么?又意味着什么?
 
Scientists have observed this phenomenon in very different animal species from wild sheep to woodrats. But it’s especially well-documented in North American songbirds.
 
从野生绵羊到林鼠,科学家已经在许多不同的动物物种中观察到了这一现象,但北美鸣禽的相关记录尤为充分。
 
In 2019, researchers at the University of Michigan published a dataset of more than 70,000 birds that died after hitting windows in Chicago. The data showed the body sizes for dozens of species had actually shrunk over the past 40 years.
 
美国密歇根大学(University of Michigan)的研究人员在2019年发表了一份数据集,记录了在美国芝加哥死于撞击窗户的7万多只鸟儿,数据显示,过去40年中有几十种鸟类的体型正在缩小。
 
But when Justin Baldwin, a graduate student at Washington University in St. Louis, took a closer look at the data … something stood out. [Justin W. Baldwin et al., Phenotypic responses to climate change are significantly dampened in big-brained birds]
 
美国圣路易斯华盛顿大学(Washington University in St. Louis)的研究生贾斯汀·鲍德温(Justin Baldwin)仔细看过数据后,发现有些细节极为突出。[Justin W. Baldwin 等人,大脑鸟类对气候变化的表型反应明显减弱]
 
Justin Baldwin: There clearly seem to be some species that were shrinking a lot and other species that were shrinking much less.
 
很明显,有些鸟类体型缩小的幅度更大,而其他的缩小幅度则相对小得多
 
Farzan: The question was … why were some bird species shrinking faster than others?
 
那么问题来了,为什么有些鸟类比其他鸟类缩水更快呢?
 
Baldwin and his colleagues had a feeling that bird behavior might be playing a role.
 
鲍德温和同事觉得鸟类行为可能对此有所影响。
 
In birds, species with bigger brains tend to be smarter and can change their behavior based on their environment. That means that they might be able to buffer themselves from increasing temperatures, says Carlos Botero, an assistant professor of biology at Washington University and the study’s co-author.
 
脑袋更大的鸟类往往更聪明,会根据所处的环境改变自己的行为,这说明它们或许能保护自己少受气温升高的影响,论文的共同作者、华盛顿大学生物助理教授卡洛斯·波特罗(Carlos Botero)解释道。
 
Carlos Botero: By adjusting their behavior, by changing the places that they look for food, the times of the day in which they do that, the things that they eat, and the ways in which they access those food sources. All those are ways in which they could experience a little bit less of a negative selection from all this variety of changes that we're seeing through climate change.
 
通过调整自己的行为,也就是改变觅食的地方、时间、对象以及获得食物资源的方式,它们就能在面对气候变暖带来的种种变化时,尽量减少自身所受的负面影响。
 
Farzan: A bigger-brained bird, for example, might adjust its behavior and stay in the shadows when it’s hot.
 
例如,脑袋更大的鸟类可能会在天热时选择停留在阴凉处。
 
So the team decided to reanalyze that massive, original dataset—but this time, factor in brain size.
 
所以,团队决定重新分析大量原始数据,但这次,主要关注的因素是大脑尺寸。
 
They found birds with larger brains in relation to their body size are shrinking at slower rates than birds with smaller brains.
 
他们发现,脑袋相对于身型更大的鸟类,体型缩小的速度慢于头脑更小的鸟。
 
And that was true even after controlling for other factors that could affect how quickly these birds are evolving, like generation time and mutation rate.
 
即使调控了可能影响鸟类演化速度的其他因素,例如世代时间、突变速率等,情况也仍然如此。
 
But Botero says, just because these larger-brained bird species can temporarily buffer themselves from warmer temperatures … it doesn’t mean they’re completely protected from climate change.
 
不过,波特罗说,脑袋更大的鸟类只能暂时缓冲更高温度的影响,这不代表它们能完全保护自己不受气候变化影响。
 
Botero: It is important to realize that what we see here is not an indication that big brain birds are fine, and that they are not having any problems or that they are just capable to take whatever kind of change is coming from this suite of different environmental phenomena that is happening right now.
 
重点是要认识到,我们这里看到的情况并不是说‘大头鸟儿’能明哲保身,不能说它们现在完全没有遇到什么问题,也不能说它们能以自身之变承受当下多种环境变化所产生的影响。
 
Farzan: Still, the team says there’s still a lot to learn when it comes to the ways in which bird behavior could affect how these species respond to climate change.
 
然而,研究团队表示,至于鸟类行为如何影响它们对气候变化的响应,他们还有很多须要了解。
 
For one thing, in this study, there was only about a twofold difference in relative brain size between the species with the largest brain—the song sparrow—and the one with the smallest—the Swainson’s Thrush.
 
一方面,这项研究中脑袋最大的鸟类(歌带鹀)和脑袋最小的鸟类(斯氏夜鸫),它们的大脑相对尺寸差异只有两倍。
 
That means the responses could be even stronger in birds with larger brains, like crows, Baldwin says.
 
这表明像乌鸦这样脑袋更大的鸟对气候的响应也许会更强烈,鲍德温补充道。
 
Baldwin: We're sampling only a small amount of the potential variation in relative brain size here in our study. And so that does suggest that even potentially small differences in relative brain size might actually have a large effect on ecological responses to climate change.
 
研究中我们只抽样调查了鸟类大脑相对尺寸中较小一部分的可能变化情况,这同时也表明,即使是大脑相对尺寸的微小差异,气候变化的生态响应也可能会给动物带来巨大的转变。
 
Farzan: For now, Baldwin says, one of their biggest takeaways is that smaller-brained bird species could be particularly vulnerable as the climate continues to change.
 
目前而言,鲍德温研究的最大收获是:面对气候的持续变化,脑袋更小的鸟类会变得特别脆弱。
 
For Scientific American’s 60-Second Science, I’m Shahla Farzan.
 
以上是《科学美国人》的 60秒科学,莎拉·法赞报道。
 
 
Shahla Farzan: This is Scientific American’s 60-Second Science. I’m Shahla Farzan.
 
Climate change is affecting animals in a lot of different ways. But scientists have noticed a common trend across a variety of species: they’re getting smaller. As in—physically smaller in size. But why, and what could this mean?
 
Scientists have observed this phenomenon in very different animal species from wild sheep to woodrats. But it’s especially well-documented in North American songbirds.
 
In 2019, researchers at the University of Michigan published a dataset of more than 70,000 birds that died after hitting windows in Chicago. The data showed the body sizes for dozens of species had actually shrunk over the past 40 years.
 
But when Justin Baldwin, a graduate student at Washington University in St. Louis, took a closer look at the data … something stood out. [Justin W. Baldwin et al., Phenotypic responses to climate change are significantly dampened in big-brained birds]
 
Justin Baldwin: There clearly seem to be some species that were shrinking a lot and other species that were shrinking much less.
 
Farzan: The question was … why were some bird species shrinking faster than others?
 
Baldwin and his colleagues had a feeling that bird behavior might be playing a role.
 
In birds, species with bigger brains tend to be smarter and can change their behavior based on their environment. That means that they might be able to buffer themselves from increasing temperatures, says Carlos Botero, an assistant professor of biology at Washington University and the study’s co-author.
 
Carlos Botero: By adjusting their behavior, by changing the places that they look for food, the times of the day in which they do that, the things that they eat, and the ways in which they access those food sources. All those are ways in which they could experience a little bit less of a negative selection from all this variety of changes that we're seeing through climate change.
 
Farzan: A bigger-brained bird, for example, might adjust its behavior and stay in the shadows when it’s hot.
 
So the team decided to reanalyze that massive, original dataset—but this time, factor in brain size.
 
They found birds with larger brains in relation to their body size are shrinking at slower rates than birds with smaller brains.
 
And that was true even after controlling for other factors that could affect how quickly these birds are evolving, like generation time and mutation rate.
 
But Botero says, just because these larger-brained bird species can temporarily buffer themselves from warmer temperatures … it doesn’t mean they’re completely protected from climate change.
 
Botero: It is important to realize that what we see here is not an indication that big brain birds are fine, and that they are not having any problems or that they are just capable to take whatever kind of change is coming from this suite of different environmental phenomena that is happening right now.
 
Farzan: Still, the team says there’s still a lot to learn when it comes to the ways in which bird behavior could affect how these species respond to climate change.
 
For one thing, in this study, there was only about a twofold difference in relative brain size between the species with the largest brain—the song sparrow—and the one with the smallest—the Swainson’s Thrush.
 
That means the responses could be even stronger in birds with larger brains, like crows, Baldwin says.
 
Baldwin: We're sampling only a small amount of the potential variation in relative brain size here in our study. And so that does suggest that even potentially small differences in relative brain size might actually have a large effect on ecological responses to climate change.
 
Farzan: For now, Baldwin says, one of their biggest takeaways is that smaller-brained bird species could be particularly vulnerable as the climate continues to change.
 
For Scientific American’s 60-Second Science, I’m Shahla Farzan.

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