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第二篇托福机经阅读是讲动物保护自己领土territory的习性，说动物生活的地区性还是什么去了。有讲到xxmale鱼在一个特定的territory里面，其他的动物过来了会攻击，male鱼在这个territory里面是为了繁殖后代。还讲到了两种鸟(sun bird 和hummingbird)，鸟在不同的territory会有不同的体重等。
解析：本文描述了动物保护领地的许多特点，属于托福常见的动物类文章结构。TPO类似的文章类型可以参见Animal Signals in The Rain Forest。考生须注意总结不同动物对于领地保护的不同特点。
Animal Territory
Territorial animals defend areas that contain a nest, den or mating site and sufficient food resources for themselves and their young. Defense rarely takes the form of overt fights: more usually there is a highly noticeable display, which may be visual (as in the red breast of the robin), auditory (as in much bird song, or the calls of gibbons) or olfactory, through the deposit of scent marks. Many territorial mammals use scent-marking to signal the boundaries of their territories; the marks may be deposited by urination, by defecation, or by rubbing parts of the bodies that bear specialisedscent glands against the substrate.
Territories may be held by an individual, a mated pair, or a group. Territoriality is not a fixed property of a species: for example, robins defend territories as pairs during the breeding season and as individuals during the winter, while some nectarivores defend territories only during the mornings (when plants are richest in nectar). In species that do not form pair bonds, male and female territories are often independent, in the sense that males defend territories only against other males, and females only against other females; in this case, if the species is polygynous, one male territory will probably contain several female territories, while in some polyandrous species such as the Northern Jacana, this situation is reversed.
Quite often territories that only yield a single resource are defended. For example, European Blackbirds may defend feeding territories that are distant from their nest sites, and in some species that form leks, for example the Uganda kob (a grazing antelope), males defend the lek site (which is used only for mating).
Ruby-throated Hummingbirds--like most hummingbird species--demonstrate strong territorial behavior; humans might even consider them to be "antisocial."
Adult male RTHUs arrive on their breeding grounds in spring and quickly establish non-overlapping feeding territories from which they drive away intruders, especially rival males. If a bluffing charge attack does not dispel a trespasser, the resident male may engage him in a brief but intense physical battle. These seldom cause physical damage other than the loss of a few feathers.
An adult male also will repeatedly drive away any female until she mates with him, after which she typically gets "free passage" into his territory. This is a great benefit to her; when she is sitting on eggs or chicks, it is important that she not be off them too long searching for food, or her offspring may die.
A male RTHU is effectively able to defend a territory of approximately a quarter-acre or so (1,000 square meters or 0.1 hectares). If the territory contains prime resources such as patches of nectar plants and/or a well-maintained artificial feeder, the bird will not have to leave his area on foraging trips. Females are known to defend nesting territories young males will defend food resources, so it's best not to assume that a defensive bird is always an adult male. Female RTHUs will forage up to half a mile in any direction from a nest--inscribing a circle of up to a mile in diameter--but it would be impossible for her to defend this area.
The territory holder usually maintains ground only by expending much time and effort in its defense. Sunbirds, for example, can expend up to 3,000 calories per hour patrolling and defending territory. Such costs can only be paid and benefits realized if there is an abundance of food to support it.
If food supplies are low, an animal may not gain enough energy to balance the energy used in defense. In such circumstances, it is not advantageous to be territorial. If food supplies are high, an animal can meet its daily energy needs without the added cost of being territorial. From an energy standpoint, defending even abundant resources usually isn’t worth the cost. Thus, territoriality usually only occurs at intermediate levels of food availability, where the benefits of defense offset the costs.
