听力文摘：千差万别的鸟蛋

Depending on the species, bird eggs can be any color ranging from chicken’s plain white to a robin’s blue, streaked¹, spotted², bright, pale, and anything in between. We take a look at some of the reasons this might be the case.

不同鸟类蛋壳的颜色千差万别，鸡蛋是纯白色，知更鸟蛋是蓝色，其它蛋壳的颜色迥异：有条纹的、有斑点的、亮色的、淡色的或者是介于之间的。那么，让我们看看颜色不一的原因吧！

But first, how do eggs get their color? As the egg moves down the female’s oviduct, the tube that connects the ovary to the outside, it squeezes against glands³ that produce colored pigments⁴ that combine to form every color in the egg shell spectrum⁵. If the egg is stationary⁶ at the time that it comes in contact with these glands, it’ll be spotted. If the egg is in motion, it will be streaked.

那么，蛋壳的颜色是如何形成的呢？鸟蛋经由母体的输卵管（连接卵巢和外界）排出，分泌色素的腺体受挤压，给蛋壳着色。如果此刻鸟蛋是静止的，触碰腺体的蛋壳形成斑点；如果是运动的，蛋壳形成条纹。

So why go through all the trouble of producing colored eggs? For many species of birds that nest out in the open, the eggs’ colors help to conceal⁷ them by enabling them to blend into the background. Another way that colored eggs come in handy, is that in some species, like murres, individual birds learn to recognize their own particular markings and reject eggs that don’t match. In contrast, birds that nest in cavities, or that start incubating as soon as the egg is laid and consequently don’t need to hide their eggs, tend to lay unmarked white ones.

为什么那么大费周章地形成不同色彩呢？一些鸟类的巢在露天野外，蛋壳的色彩有助于和外界混为一体，便于隐藏。蛋壳颜色还在某些地方能排上用场：例如海鸦，通过蛋壳颜色来识别，排除它类。另外一些鸟类在树洞中筑巢的，或下蛋后马上孵化的；鸟蛋不用隐藏，蛋壳颜色通常是白色。

Given all this, how do scientists explain the fact that robin’s eggs are an eye-catching, unmarked blue? Perhaps this enables robins⁸ to spot when a parasitic⁹ bird tries to add its own eggs to the nest. For some species, this may pose a greater threat than that of nest robbers.

终上所述，科学家如何解释知更鸟蛋是耀眼的纯蓝色呢？也许这样便于知更鸟识破其巢寄生的鸟类将自己蛋放进知更鸟巢吧！巢寄生的行为对其他鸟类更具威胁性！

1 streaked   

adj.有条斑纹的，不安的v.快速移动( streak的过去式和过去分词 )；使布满条纹

参考例句：

• The children streaked off as fast as they could. 孩子们拔脚飞跑 来自《现代英汉综合大词典》
• His face was pale and streaked with dirt. 他脸色苍白，脸上有一道道的污痕。 来自辞典例句

2 spotted   

adj.有斑点的，斑纹的，弄污了的

参考例句：

• The milkman selected the spotted cows,from among a herd of two hundred.牛奶商从一群200头牛中选出有斑点的牛。
• Sam's shop stocks short spotted socks.山姆的商店屯积了有斑点的短袜。

3 glands   

n.腺( gland的名词复数 )

参考例句：

• a snake's poison glands 蛇的毒腺
• the sebaceous glands in the skin 皮脂腺

4 pigments   

n.（粉状）颜料( pigment的名词复数 )；天然色素

参考例句：

• The Romans used natural pigments on their fabrics and walls. 古罗马人在织物和墙壁上使用天然颜料。 来自辞典例句
• The original white lead pigments have oxidized and turned black. 最初的白色铅质颜料氧化后变成了黑色。 来自辞典例句

5 spectrum   

n.谱，光谱，频谱；范围，幅度，系列

参考例句：

• This is a kind of atomic spectrum.这是一种原子光谱。
• We have known much of the constitution of the solar spectrum.关于太阳光谱的构成，我们已了解不少。

6 stationary   

adj.固定的，静止不动的

参考例句：

• A stationary object is easy to be aimed at.一个静止不动的物体是容易瞄准的。
• Wait until the bus is stationary before you get off.你要等公共汽车停稳了再下车。

7 conceal   

v.隐藏，隐瞒，隐蔽

参考例句：

• He had to conceal his identity to escape the police.为了躲避警方，他只好隐瞒身份。
• He could hardly conceal his joy at his departure.他几乎掩饰不住临行时的喜悦。

8 robins   

n.知更鸟，鸫( robin的名词复数 )；（签名者不分先后，以避免受责的）圆形签名抗议书（或请愿书）

参考例句：

• The robins occupied their former nest. 那些知更鸟占了它们的老窝。 来自《现代汉英综合大词典》
• Benjamin Robins then entered the fray with articles and a book. 而后，Benjamin Robins以他的几篇专论和一本书参加争论。 来自辞典例句

9 parasitic   

adj.寄生的

参考例句：

• Will global warming mean the spread of tropical parasitic diseases?全球变暖是否意味着热带寄生虫病会蔓延呢？
• By definition,this way of life is parasitic.从其含义来说，这是种寄生虫的生活方式。