英语听力文摘 单腿站立的鸟
Cold Feet and Hot Wings
鸟通常只在休息或睡觉的时候才单脚站立。鸟类学家认为，他们这么做是为了减少能量的消耗，并把一只脚收到翅膀之下休息，通常他们会交替使用两只脚"独立"。披着一身羽毛，羽毛能帮助它保持身体的温度。但是它的腿、脚以及喙上却不长毛，体内的热量很容易从腿脚散失，为了减少热量散失，休息时经常抬起一只脚，藏在羽毛下面。这也是为什么鸟类有时还向后弯曲脖颈，把喙埋在羽毛中的原因，因为这样做也有利于防止散热。
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(水鸟), 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 坐着不做事;懒散地消磨时间
The people don't really work out there. They just stand around and talk all the time.
那儿的人根本不练习。他们只是站在一旁光滔滔不绝地说而已。
(2)tuck up 折起,卷起
The man tucked up his trousers for wading.
那人捲起裤子，准备涉水。
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