Аудирование TOEFL

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Listen to part of a lecture in a biology class. The professor is discussing the behavior of certain birds. Professor: Today, let’s talk about a fascinating behavior known as mobbing, which is common among small birds. When a predator, like a hawk or a crow, is spotted, smaller birds such as chickadees and titmice will gather around it, making loud calls and diving at it. At first glance, this seems risky—why would a small bird put itself in danger? Well, researchers have found that mobbing serves several purposes. First, it can drive the predator away, especially if the predator is not particularly hungry or if it’s a young predator that might be easily intimidated. Second, mobbing alerts other birds in the area to the presence of danger, allowing them to take cover or join the mob. Interestingly, studies show that the intensity of mobbing varies. For example, birds mob more aggressively when they have nests nearby, because the threat to their offspring is higher. Also, the type of predator matters—birds mob owls more intensely than hawks, possibly because owls are nocturnal and more likely to sneak up on nests at night. So, mobbing is not just a simple reaction; it’s a complex strategy that balances risk and benefit.