填空题 .  Bird Territoriality
    Like most animals, birds possess the desire to control the territory in which they live. Ornithologists refer to this area, where the bird conducts its normal daily activities, as its home range. The size of the home range depends on the species. Large birds of prey, including eagles and hawks, may possess home ranges covering dozens of square kilometers while many seabirds defend only a small space found in the immediate vicinity of their nests. Some birds may be slack in defending their home ranges but may become quite aggressive during the breeding season and when eggs are in their nests. Birds typically defend their home ranges the most aggressively against other birds of the same species but may also react belligerently to transgressions made by other species of birds or other types of animals.
    Birds normally defend their home ranges for three primary purposes: to protect their food sources, to compete for mates when breeding, and to defend nests full of eggs or chicks against predators. Hummingbirds, for instance, defend prime sources of nectar from other hummingbirds as well as insects that consume it. Male grouses defend the small patches of ground they use for breeding displays to attract females from other males of their species. And penguins aggressively defend the patches of seashore where they lay their eggs when predatory birds approach.
    When defending territory, few birds actually make physical contact with one another but instead utilize warnings such as the songs of male birds. These songs inform other birds that a male has claimed a specific area of land. If, however, the songs are ineffective, a bird may make a prominent display of aggressive posturing, which may include spreading its wings and puffing up its body. Should this not work, the aggrieved bird may give chase, and actual fighting sometimes occurs. In most cases, fighting happens when birds are defending their nests against predators such as lizards, snakes, and small mammals intent on consuming their eggs or chicks.
    *ornithologist: a person who studies birds
    *belligerently: aggressively13.  In paragraph 1, the author uses eagles and hawks as examples of ______