时差N小时 为什么鸟类的羽毛颜色进化跟饮食有关?

Sometimes it's easy to understand how an evolutionary¹ change took place, but it's more difficult to understand why.

有时候去理解生物进化演变的过程很容易，想知道原因却很难。

For example, consider the beautiful birds of paradise which live in the forests of New Guinea. The males of many bird-of-paradise species have evolved colorful plumage, used for dramatic courtship displays. How this plumage evolved is no mystery: The healthiest males usually have the most spectacular plumage, so females choose whichever male has the gaudiest² feathers. With this criterion, it's not surprising that male plumage would grow more and more elaborate over the generations.

就拿居住在新几内亚森林中的极乐鸟作例子吧。极乐鸟种群中的雄性常常会利用它们绚丽多彩的羽毛上演一幕又一幕的求爱话剧。这羽毛是怎样进化来的并不神秘：最健壮的雄性往往拥有最绚丽的羽毛，所以雌性往往会选择有艳丽羽毛的雄性。在这种标准的要求下，雄性鸟儿拼命想长出比同类更抢眼，更精致的羽毛，这一点不足为奇。

Understanding why the plumage evolved is a little trickier³. After all, there are some bird-of-paradise species that are really quite drab. These birds devote most of their energy to finding food and raising their young, instead of wasting it on courtship. What makes these near neighbors so different?

了解羽毛色泽为什么会进化就有点棘手了。毕竟，有几种极乐鸟的颜色十分单调。这些鸟把它们主要的精力都放在寻找食物和抚养后代上了，而不是用于求爱。是什么导致这些近邻如此不同？

The answer is diet. Those species with the most elaborate plumage also have the most diverse and reliable diet: a variety of insects, and fruits rich in complex nutrients⁴. With this healthy, reliable food supply, females can raise the hatchlings without help from the males. This frees the males for their extravagant⁵ courtship behavior, and the complex diet provides them with chemicals to make their brightly colored feathers.

答案就是日常饮食。那些有着最美丽羽毛的鸟儿有各式各样并且稳定的食物：各种昆虫和富含多种营养的水果。有了这种健康的、可靠的食物供应，雌性极乐鸟可以完全不依靠雄性而独立抚养后代。这样就使得雄性有闲暇时间去发展求爱行为，而且多样饮食中的化学物质能让他们的羽毛更鲜亮。

In contrast, the drabber birds have a limited diet of simple figs⁶, which are available more sporadically⁷. They're monogamous, and both parents need to spend most of their time foraging⁸. This means less time for elaborate courtship behavior.

与此相反，拥有单调毛色的鸟儿的食谱就相对简单，仅限于零星分布的无花果。同时它们实行一夫一妻制，父母双方都需要花费大量的时间寻找食物，这就大大缩短了用于考虑花哨的求爱方式的时间。

So different diets lead to different behaviors, which results in the evolution of different plumage. These exotic birds show just how complex evolution can be!

所以，不同的食物产生不一样的生活方式，也是进化出不同毛色的原因。这些奇异的鸟儿向我们解释了进化有多么复杂！

1 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。

2 gaudiest   

adj.花哨的，俗气的( gaudy的最高级 )

参考例句：

• The witch doctors were bedizened in all their gaudiest costumes. 女巫医穿上她们最绚丽的衣服，打扮得俗不可耐。 来自辞典例句

3 trickier   

adj.狡猾的( tricky的比较级 )；（形势、工作等）复杂的；机警的；微妙的

参考例句：

• This is the general rule, but some cases are trickier than others. 以上是一般规则，但某些案例会比别的案例更为棘手。 来自互联网
• The lower the numbers go, the trickier the problems get. 武器的数量越低，问题就越复杂。 来自互联网

4 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》

5 extravagant   

adj.奢侈的；过分的；(言行等)放肆的

参考例句：

• They tried to please him with fulsome compliments and extravagant gifts.他们想用溢美之词和奢华的礼品来取悦他。
• He is extravagant in behaviour.他行为放肆。

6 figs   

figures 数字，图形，外形

参考例句：

• The effect of ring dyeing is shown in Figs 10 and 11. 环形染色的影响如图10和图11所示。
• The results in Figs. 4 and 5 show the excellent agreement between simulation and experiment. 图4和图5的结果都表明模拟和实验是相当吻合的。

7 sporadically   

adv.偶发地，零星地

参考例句：

• There are some trees sporadically around his house. 他的房子周围零星地有点树木。 来自辞典例句
• As for other aspects, we will sporadically hand out questionnaires. 在其他方面，我们会偶尔发送调查问卷。 来自互联网

8 foraging   

v.搜寻（食物），尤指动物觅（食）( forage的现在分词 )；（尤指用手）搜寻（东西）

参考例句：

• They eke out a precarious existence foraging in rubbish dumps. 他们靠在垃圾场捡垃圾维持着朝不保夕的生活。 来自《简明英汉词典》
• The campers went foraging for wood to make a fire. 露营者去搜寻柴木点火。 来自辞典例句