Official 11 Set 2

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Parenting Behavior of Birds

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What is the talk mainly about?
  • A. Various predators that threaten young birds

  • B. Various patterns of growth in young birds

  • C. One way that birds protect their young

  • D. One way that birds provide food for their young

显示答案 正确答案: C

我的笔记 编辑笔记

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    NARRATOR:Listen to part of a lecture in a biology class. The class has been learning about birds.

    FEMALE PROFESSOR:OK, today we are going to continue our discussion of the parenting behaviors of birds.And we are going to start by talking about what are known as "distraction displays".Now if you are a bird, and there was a predator around, what are you going to do?Well, for one thing, you are going to try to attract as little attention as possible, right?Because if the predator doesn't know you are there, it's not going to try to eat you.But sometimes, certain species of birds do the exact opposite.When the predator approaches, they do their best to attract the attention of that predator.[not a question]Now why would they do that?Well, they do that to draw the predator away from their nests, away from their eggs or their young birds.And the behaviours that the birds engage in to distract predators are called "distraction displays".And there are a number of different kinds of distraction displays.Most of the time, when birds are engaging in distraction displays, they are going to be pretending…either that they have injury…or that they are ill…or that they are exhausted…You know something that will make the predator think, “Oh, here’s an easy meal.”One pretty common distraction display is what's called the "broken-wing display".And in a broken-wing display, the bird spreads and drags a wing or its tail, and while it does that, it slowly moves away from the nests, so it really looks like a bird with a broken wing.And these "broken-wing displays" can be pretty convincing.

    Another version of this kind of "distraction display" is where the birds create the impression of a mouse or some other small animals that's running around the ground.A good example of that kind of display is created by a bird called "the purple sandpiper".Now what the purple sandpiper does is when a predator approaches, it drags its wings, but not to give it the impression that its wings is broken,but to create the illusion that it has a second pair of legs.And then it raises its feathers, so it looks like it's got a coat of fur.And then it runs along the ground swirling left and right, you know like it's running around little rocks and sticks.And as it goes along it makes a little squealing noises.So from a distance it really looks and sounds like a little animal running along the ground trying to get away.Again, to the predator, it looks like an easy meal.Now, what's interesting is that birds have different levels of performance of these distraction displays.They don't give their top performance, their prime time performance every time.What they do is, they save their best performances, their most conspicuous and most risky displays, for the time just before the baby birds become able to take care of themselves.And they time it that way because that's when they'll have made the greatest investment in parenting their young.So they’re not going to put on their best performance just after they’ve laid their eggs, because they haven’t invested that much time or energy in parenting yet.The top performances are going to come later.Now you have some birds that are quite mature, quite capable, almost as soon as they hatch. In that case, the parent will put on the most conspicuous distraction displays just before the babies hatch.Because once the babies are hatched, they can pretty much take care of themselves.And then you have other birds that are helpless when they hatch.In that case, the parent will save its best performances until just before the babies get their feathers.

  • 旁白:听下面一段的生物课程,这门课程在学习鸟类。

    教授:好的,今天我们要继续讨论关于鸟类的哺育行为。首先我们来谈谈什么是distractiondisplays。现在,如果我们是鸟,而周围正有一个捕食者者,我们会做什么?首先,你会想要尽量不引起它的注意,对吗?因为捕猎者如果不知道你在那儿,就不会试着吃掉你。但有些鸟类的行为恰恰相反。当捕食者靠近的时候,它们想方设法去吸引它的注意力。为什么它们会这么做?它们这么做,是为了将捕食者从它们的巢和里面的幼鸟吸引走。这种调离注意力的行为,就叫做分散注意力行为(distraction displays)。有很多种鸟类分散捕食者注意力的方法。大多数时间,当一个鸟要进行分散注意力行为的时候,它们会或者假装是受伤了,或者假装是生病了非常疲惫。你知道⋯⋯就是任何一种能让捕食者认为“嗯,这个猎物很好得手”的行为。一种比较常见的分散注意力的方法叫做“断翅法”。在“断翅法”中,一只鸟会散开它的翅膀和尾巴,拖拽着移动,它一边这么做,一边慢慢远离自己的巢,所以它看起来真的像一只翅膀折断的鸟。而这些“断翼展示”可能相当令人信服。

    另外一种版本的分散注意力,是鸟类制造了一种假象,好像有老鼠等小动物正在周围。这种行为的一个很好的例子是由一种叫做紫矶鹞(purple sand piper)的鸟类演绎的。当一个捕食者在周围时,紫矶鹞做的是,拖拽着翅膀但并不是要假装翅膀断了而是为了制造一种(翅膀下面)有另外一双脚的错觉。然后它竖起羽毛,看起来好像有一层皮毛。然后它沿着地面左右旋转,你知道就像它绕着小石头和树枝跑。当它前进的时候会发出一些吱吱的声音。所以从远处看,的确很像是一个小动物在地上逃跑的样子。同样,这会让捕食者觉得,这是一顿能轻易得手的晚饭。有趣的是鸟类对这些分散注意力的表现有不同程度的表现。它们并不是每次都拿出它们最高超的的手段示人。它们在风险达到顶峰的时刻才会使用最厉害的方法,而当幼鸟即将出巢并且有了自理能力的时候,它们所使用的分散注意力的手段就会是(比较粗糙,甚至有点)冒险的。因为保护幼鸟需要合理地投入精力。所以当鸟类刚下蛋后,它们不会花太多精力做分散注意力的行为,因为它们还有花费更多的精力去哺育幼鸟。高招要稍后再出。而现在,一些幼鸟已经长的比较成熟了,也将在被孵育出的一刻能够自理,这种情况下,它们的父母将上演最显眼的分散精力术,在幼鸟即将破壳之前。因为一旦它们破壳而出,就可以照顾自己了。还有其他的鸟在孵化的时候是无助的。这样,父母就会将最好的分散注意力术一直上演到幼鸟长出羽毛。

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    题型分类:主旨题
    原文定位:

    OK, today we are going to continue our discussion of the parenting behaviors of birds. And we are going to start by talking about what are known as distraction displays.

    选项分析:
    开头用talk about引出要讲的distraction displays,而后续对distraction displays的解释,表明这是一种成年鸟保护幼鸟的方法,C正确。

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