Grassland songbirds often nest in the same grassland-wetland complexes

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 nest. 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 waterfowl-nest predators, primarily 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.

1. According to the passage, which of the following is true about the role played by ground squirrels in the ecology of grassland-wetland complexes?

(A) While not important in the diet of raccoons or striped skunks, ground squirrels are a significant source of food for other waterfowl-nest predators.
(B) 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.
(C) 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.
(D) 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.
(E) 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.



2. Which of the following best describes the function of the sentence “Neither raccoons…songbird nests” in the context of the passage as a whole?

(A) It raises questions about the validity of a theory described in the first paragraph.
(B) It points out an oversimplification that is inherent in the argument presented in the first paragraph.
(C) It introduces information that may help explain the results of the experiment that are presented earlier in the paragraph.
(D) It provides a specific example of the type of data collected in the experiment described earlier in the paragraph.
(E) It anticipates a potential objection to the conclusions drawn by the researchers involved in the experiment described earlier in the paragraph.



3. The primary purpose of the passage is to

(A) describe some procedures used for wildlife management and consider some problems associated with the execution of those procedures
(B) outline a problem related to a wildlife management procedure and offer potential explanations for the results of an experiment bearing on that problem
(C) present experimental results that illustrate the need for certain wildlife management procedures and point out some inconsistencies in those results
(D) argue that a certain procedure used for wildlife management should be modified because of its unintended consequences
(E) propose that further experiments be performed to assess the long-term effects of certain wildlife management procedures



4. The passage suggests that removing waterfowl-nest predators could possibly have a negative effect on songbird populations because

(A) songbird populations could then grow to unsustainable numbers
(B) small-mammal population could then move out of the uplands into wetland areas
(C) competition among remaining waterfowl-nest predators could decrease significantly
(D) a resulting increase in waterfowl populations could crowd out songbird populations
(E) a resulting increase in small-mammal populations could increase small-mammal predation on songbirds



5. It can be inferred that the habitat preferences of raccoons and striped skunks affected the results of the experiment described in the passage for which of the following reasons?

(A) Songbird nests in the wetlands are usually located in places that most waterfowl-nest predators cannot reach.
(B) Raccoons and striped skunks are not usually found in areas where songbird nests tend to be located.
(C) Mice and ground squirrels tend to avoid predation by raccoons and striped skunks by remaining exclusively in the uplands.
(D) The populations of small mammals in the wetlands are usually controlled by larger waterfowl-nest predators such as raccoons and striped skunks.
(E) The waterfowl on which raccoons and striped skunks prey in the wetlands compete with songbirds for food.