【英语时差8,16】为什么鸟类的羽毛与它们的饮食有关

 

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

  

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.

 

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?

 

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.

 

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.

 

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!  

 

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