TOEFLリスニング

🎧 リスニング原文

Listen to part of a lecture in a biology class. The professor is discussing the behavior of certain bird species. "Today, we're going to talk about a fascinating phenomenon called 'mobbing' in birds. When a predator, such as a hawk or a crow, is spotted, smaller birds often gather and harass it by diving and calling loudly. This behavior may seem risky, but it serves several purposes. First, it alerts other birds in the area to the danger. Second, it can drive the predator away, especially if the predator is not hungry or is outnumbered. Interestingly, research shows that birds are more likely to mob a predator that is perched, rather than one that is flying. Why? Because a perched predator is more predictable and less dangerous to approach. Additionally, the intensity of mobbing increases when the predator is near the birds' nests. Some scientists believe that mobbing also helps young birds learn to identify potential threats. However, there are costs: mobbing attracts attention and may expose the mobbers to attack. Despite this, the benefits usually outweigh the risks, as mobbing increases the survival chances of the group and their offspring." Now the professor describes a specific experiment. "In a recent study, researchers used a stuffed owl as a model predator. They observed that birds mobbed the owl more aggressively when it was placed near nests with chicks. This supports the idea that mobbing is a protective response."