【正确答案】Key points: Competition is the struggle over scarce resources. The lecture discusses direct and indirect competition. Direct competition is when a bird actively excludes others from getting resources. Examples are stealing food, establishing territories, and fighting. Indirect competition is when birds simply use up a resource so others can not use that resource. An example is a flock of geese eating all the food in an area. (3.9, 3.10) [听力原文] Competition is the struggle over scarce resources. Whenever there's a limited supply of a resource--such as food, nesting sites, or mates--there will be competition. Competition can take place between birds of the same species or between birds of different species. There are two forms of competition: direct and indirect. Direct competition is when a bird actively excludes others from getting resources. A common example is stealing. One bird may simply take food from another. Another example is establishing territories. Especially during the breeding season, birds maintain and defend some sort of territory. They form territories to defend resources like food, or to maintain access to good nesting sites, or to attract mates. Some birds compete directly by fighting, for example, when they compete for mates. Others fight over food. You can see this if you watch gulls feeding on the garbage at the local dump. The second type of competition is indirect. Indirect competition is when birds simply use up a resource. When one species eats all the seeds or berries or grubs, this will prevent other species from using that resource. Indirect competition is less open than direct competition, but it can have just as great an influence on populations. For example, a flock of geese grazing in a field will gradually decrease the amount of food there. The larger the flock, the faster the food will be consumed, and this will reduce the amount of food available for other species.