英語(yǔ)聽(tīng)力文摘 單腿站立的鳥(niǎo)
Cold Feet and Hot Wings
鳥(niǎo)通常只在休息或睡覺(jué)的時(shí)候才單腳站立。鳥(niǎo)類學(xué)家認(rèn)為，他們這么做是為了減少能量的消耗，并把一只腳收到翅膀之下休息，通常他們會(huì)交替使用兩只腳"獨(dú)立"。披著一身羽毛，羽毛能幫助它保持身體的溫度。但是它的腿、腳以及喙上卻不長(zhǎng)毛，體內(nèi)的熱量很容易從腿腳散失，為了減少熱量散失，休息時(shí)經(jīng)常抬起一只腳，藏在羽毛下面。這也是為什么鳥(niǎo)類有時(shí)還向后彎曲脖頸，把喙埋在羽毛中的原因，因?yàn)檫@樣做也有利于防止散熱。
Most birds you see standing on only one leg are doing an impressive balancing act while tucking the second leg into their feathers. This is much easier to recognize in large birds, such as flamingos, but the behavior itself is common to most birds. So, the real question is: why do they do that?
The answer is that birds use their feet for temperature regulation. In most birds the legs and feet are unfeathered, and thus lose heat very quickly — the same way your exposed hands get cold in winter faster than your clothing-covered torso. That makes the bare feet great conductors: when the bird’s overall body temperature is too high, it can cool off by standing on both legs and letting the wind carry away heat. When the temperature drops too low, it can pull one leg up and lose less heat.
Finally, it can sit down and cover ll the bases.
Many birds are able to control the amount of blood flow through their legs, which increases their ability to regulate temperature. The only danger comes in (1)standing around on a cold day: with one foot (2)tucked up and blood flow greatly reduced to the other, there is a possibility that the exposed leg will freeze. This can be countered by staying in a nest or, in aquatic birds(水鳥(niǎo)), by going into the water. As long as the water is in a liquid state, the bird legs floating in it can’t freeze.
Notes:
(1)stand around 坐著不做事;懶散地消磨時(shí)間
The people don't really work out there. They just stand around and talk all the time.
那兒的人根本不練習(xí)。他們只是站在一旁光滔滔不絕地說(shuō)而已。
(2)tuck up 折起,卷起
The man tucked up his trousers for wading.
那人捲起褲子，準(zhǔn)備涉水。
