2014年12月6日托福考试阅读真题回顾解析(第一版)

in the different forces generated by the rotation of the globe and the tidal forces of the Sun and Moon. The relative importance of each of these factors and their relationship to each other is unclear, and still the subject of much debate.

　　第三篇：bird colonize

　　题材划分：生物类

　　主要内容：

　　群体生活的优势和缺点。举了几个特别的鸟。其中有一类鸟，窝在悬崖边，并且是群体攻击捕食者，把空的窝和在用的混在一起。还有一种群体，同时在某一时刻生很多幼鸟。缺点是：在某个海边，很多食物适合海鸟，然后很多海鸟聚集在那里，海鸟多了，在气候变化时数量就会crash。

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　　相关知识背景

　　Ninety-five percent of seabirds are colonial, and seabird colonies are amongst the largest bird colonies in the world, providing one of Earth's great wildlife spectacles. Colonies of over a million birds have been recorded, both in the tropics (such as Kiritimati in the Pacific) and in the polar latitudes (as in Antarctica). Seabird colonies occur exclusively for the purpose of breeding; non-breeding birds will only collect together outside the breeding season in areas where prey species are densely aggregated.

　　Seabird colonies are highly variable. Individual nesting sites can be widely spaced, as in an albatross colony, or densely packed as with a murre colony. In most seabird colonies, several different species will nest on the same colony, often exhibiting some niche separation. Seabirds can nest in trees (if any are available), on the ground (with or without nests), on cliffs, in burrows under the ground and in rocky crevices. Competition can be strong both within species and between species, with aggressive species such as sooty terns pushing less dominant species out of the most desirable nesting spaces. The tropical Bonin petrel nests during the winter to avoid competition with the more aggressive wedge-tailed shearwater. When the seasons overlap, the wedge-tailed shearwaters will kill young Bonin petrels in order to use their burrows.

　　Many seabirds show remarkable site fidelity, returning to the same burrow, nest or site for many years, and they will defend that site from