Grassland songbirds often nest in the same grassland-wetland complexes as waterfowl, particularly in a certain part of those complexes, namely, upland habitats surrounding wetlands. Although some wildlife management procedures directed at waterfowl, such as habitat enhancement or restoration, may also benefit songbirds , the impact of others, especially the control of waterfowl predators, remains difficult to predict. For example, most predators of waterfowl nests prey opportunistically on songbird nests, and removing these predators could directly increase songbird nesting success. Alternatively, small mammals such as mice and ground squirrels are important in the diet of many waterfowl-nest predators and can themselves be important predators of songbird nets. Thus. Removing waterfowl-nest predators could affect songbird nesting success through subsequent increases in small-mammal populations.
In 1995 and 1996, researchers trapped and removed certain waterfowlnest predators. primary raccoons and striped skunks, then observed subsequent survival rates for songbird nests. Surprisingly. They observed no significant effect on songbird nesting success. This may be due to several factors. Neither raccoons nor striped skunks consume ground squirrels, which are important predators of songbird nests. Thus, their removal may not have led to significant increases in populations of smaller predators. Additionally, both raccoons and striped skunks prefer wetlands and spend little time in upland habitats; removing these species may not have increased the nesting success of songbirds in the uplands enough to allow detection.
According to the passage, which of the following is true about the role played by ground squirrels in the ecology of grassland-wetland complexes?
While not important in the diet of raccoons or striped skunks, ground squirrels are a significant source of food for other waterfowl-nest predators.
Whereas ground squirrels are typically important as predators of songbird nests, their opportunistic predation on waterfowl nests also has an observable effect on waterfowl nesting success.
Although most waterfowl-nest predators prey on small mammals such as mice and ground squirrels, populations of ground squirrels tend to increase quickly enough to compensate for this level of predation.
Although ground squirrels have been known to prey on songbird nests, a larger portion of their diets is usually provided by predation on waterfowl nests.
Since larger predators tend to prefer small mammals to songbird eggs as a food source, a large population of ground squirrels plays an important role in controlling opportunistic predation on songbird nests.
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正确答案是 A。
A正确,因为文章指出,尽管土拨鼠和条纹獾不会把土拨鼠当作食物,但其他水鸟巢的捕食者可能会使土拨鼠成为重要的食物来源。
1、Alternatively, small mammals such as mice and ground squirrels are important in the diet of many waterfowl-nest predators and can themselves be important predators of songbird nets.
2、Neither raccoons nor striped skunks consume ground squirrels, which are important predators of songbird nests
简直就是原文
Alternatively, small mammals such as mice and ground squirrels are important in the diet of many waterfowl-nest predators
Alternatively, small mammals such as mice and ground squirrels are important in the diet of many waterfowl-nest predators and can themselves be important predators of songbird nets.
Neither raccoons nor striped skunks consume ground squirrels, which are important predators of songbird nests
这篇文章的重点是,waterfowl水禽和songbird鸣禽是两种动物;raccoon这些是waterfowl-nest predators,主要吃waterfowl,临时起意吃songbird;ground squirrel这些是small mammal,主要被raccoon他们吃,然后主要吃songbird。
移除raccoon之后,songbird没影响,其中一个原因是raccoon不吃ground squirrel。
这很奇怪欸 raccoons or striped skunks被removed 没人去吃small mammals 所以songbird仍没有提高存活率 A选项怎么说ground squirrels不是important diet 呢 不明白 求解
我开始也被套进去了。a选项的意思是虽然raccons和skunks不吃squirrels,但是squirrels还是waterfowl的重要捕食者。
不是squirrel仍然是水禽捕食者的食物来源吗
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Alternatively, small mammals such as mice and ground squirrels are important in the diet of many waterfowl-nest predators and can themselves be important predators of songbird nets.