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  3. Recently, researchers investigated the foraging profiles of bird species in two separate eucalyptus forests in Australia: Dryand

Recently, researchers investigated the foraging profiles of bird species in two separate eucalyptus forests in Australia: Dryand

admin2021-09-28  44
问题     Recently, researchers investigated the foraging profiles of bird species in two separate eucalyptus forests in Australia: Dryandra in Western Australia and the Southern Tablelands, roughly 3000 km west in New South Wales. Despite their geographical separation, there is a broad overlap in species between the two locations. However, at Dryandra, a much larger proportion of species (61 percent) than at the Southern Tablelands (34 percent) are ground foragers.
    The high proportion of ground foragers in Dryandra might be explained by the openness of habitats there, that is, the absence of dense ground vegetation, and the lack of a continuous shrub layer. Ground foraging appears to be facilitated by an open habitat with area of bare ground. However, the researchers found that the Tablelands were also open with sparse to dense litter layers, abundant in woody debris, and had discontinuous or absent ground and shrub layers. Thus, differences in habitat structures between these areas and Dryandra cannot entirely explain the greater abundance of ground foragers in Dryandra.
    The researchers offered several hypotheses to explain the difference. First, there may be important differences in habitat structure that are not revealed by casual observation. For example, differences in tree heights and canopy complexity may contribute to differences in species richness and foraging behavior among bark- and foliage-foraging birds. Second, despite structural similarities, it is possible that there are differences between habitats in the abundance or availability of litter and ground-dwelling prey. Such differences, if they exist, may indicate fundamental differences between eucalypt ecosystems in how and where energy and nutrients are cycled, as well as in overall productivity. Finally, the differences in foraging profiles between Dryandra and Tablelands may be the result of historical changes in bird species as a consequence of changed grazing and fire regimens, the impact of introduced predators, such as foxes and feral cats, and logging following European settlement. The greatest impact of these processes is on ground-foraging and ground-nesting birds. Dryandra has not been free of these changes, but the impact may have been less or more recent with the result that Dryandra may retain a more natural or complete bird diversity relative to the Tablelands.
The author suggests which of the following about “foxes and feral cats”
选项 A、They may have benefited from the logging that followed European settlement.
B、They probably affect the overall productivity of the ecosystem
C、They feed primarily on ground-foraging birds.
D、They rarely, if ever, feed on tree-nesting birds.
E、They may have had a smaller impact on Dryandra than on the Tablelands.
答案E
解析 根据第三段六到八句，狐狸和山猫属于外来影响的一种，它们会影响地面觅食者的数量：德兰德拉林地经受了这种影响，但是经受得比较晚，因此鸟类多样性方面比南部高原更天然和完整。所以选项E正确。C项根据第三段第七句可知，狐狸和山猫确实会以地面觅食鸟类为食，但看不出来是不是“主要”以这些鸟类为食。
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