托福听力TPO11听力文本(Conversation+Lecture)

　　TPO 11 Lecture 1

　　Biology

　　Narrator

　　Listen to part of a lecture in a Biology Class. The class has been learning about birds.

　　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 were 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 is 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 try to attract the attention of that predator. 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 behaviors that the birds engaging 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 displace they are going to be pretending either that they have injury or that they’re ill or that they’re exhausted. You know something that’ll make the predator thinks Hum… here is an easy meal. One pretty common distraction display was called the broken wing display. And in a broken wing display the bird spreads and drags the wings 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 same impression of a mouse or some other small animals that running along the ground. A good example of that kind of display is created by a bird called the purple sandpiper. Now what’s the purple sandpiper does is when a predator approaches, it drags its wings but not to give it the impression that its wings are 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 got a coat of fur. And then it runs along the ground swirling left and right you know like running around a little rocks and sticks. And as it goes along it makes a little squeezing 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 the 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 they’re most conspicuous and most risky displays for the time just before the baby birds become able to take care of themselves. And the time that way because that when that make the greatest investment in parenting their young. So they are not going to put their best performance just after they laid their eggs because they have to invest that much more time and energy in parenting yet. The top performance is going to come later. Now you have some birds that are quiet mature, are quite capable almost as soon as they hatch. In that case, the parent will put on the most conspicuous distractions displays just before the babies’ hatch because once the babies are hatch they can pretty much take care themselves, and then you have others birds that helpless when have hatch. In that case, the parents will save the best performance until just before the babies get their feathers.