Migratory North American songbirds like the Tennessee warbler and the

Question

Migratory North American songbirds like the Tennessee warbler and the Baltimore oriole depend on the dense tree cover that has long been a feature of South American coffee plantations. This tree cover is being eliminated. Yet a population decline among Tennessee warblers is being attributed to a temporary drop in the population of spruce budworms, the warbler’s favorite North American prey. Baltimore orioles, however, do not eat budworms and are also experiencing a population decline.

The information above, if accurate, could best serve as part of an argument that

The information above, if accurate, could best serve as part of an argument that

A. the decline in the numbers of the Tennessee warbler is responsible for the decline in the population of the spruce budworm

B. the Tennessee warbler population will not rebound when the spruce budworm population returns to normal

C. variations in the population of the Tennessee warbler influence the numbers of the Baltimore oriole

D. the population of Tennessee warblers can reasonably be expected to increase in the near future

E. the population of Tennessee warblers is declining less sharply than the population of Baltimore orioles

MartyMurray · Answer

Migratory North American songbirds like the Tennessee warbler and the Baltimore oriole depend on the dense tree cover that has long been a feature of South American coffee plantations. This tree cover is being eliminated. Yet a population decline among Tennessee warblers is being attributed to a temporary drop in the population of spruce budworms, the warbler’s favorite North American prey. Baltimore orioles, however, do not eat budworms and are also experiencing a population decline.

The information above, if accurate, could best serve as part of an argument that

The information above, if accurate, could best serve as part of an argument that

This is a Conclusion question. So, the correct answer will be the choice that is clearly supported by information presented by the passage.
 
A. the decline in the numbers of the Tennessee warbler is responsible for the decline in the population of the spruce budworm

This choice in a sense reverses what's said in the passage.

The passage says that the decline in the warbler population is "being attributed to" the decline in the budworm population, not that the decline in the warbler population has caused the decline in the budworm population.

Eliminate.

B. the Tennessee warbler population will not rebound when the spruce budworm population returns to normal

This choice is interesting.

The passage says that tree cover that the warblers "depend on" is being eliminated.

So, even if the budworm population recovers, it makes sense to conclude the the warbler population will not.

Keep.

C. variations in the population of the Tennessee warbler influence the numbers of the Baltimore oriole

The passage does not indicate that any such cause-effect connection between the populations exists.

Eliminate.

D. the population of Tennessee warblers can reasonably be expected to increase in the near future

The choice is tricky.

The passage does say that "a population decline among Tennessee warblers is being attributed to a temporary drop in the population of spruce budworms."

So, we might be tempted to conclude that, since the budworm population drop is "temporary," the population of warblers can reasonably be expected to increase in the near future.

At the same time, the passage also says that the tree cover that warblers depend on is "being eliminated." That information indicates that, even though the warbler population decline "is being attributed to," in other words, is believed to be caused by, the decline in the budworm population, there's actually something else going on, the elimination of tree cover that warblers depend on.

What's logical is that the elimination of that tree cover will likely cause a long-term reduction in the warbler population.

So, given that information about the tree cover, it doesn't make sense to conclude that the warbler population can be reasonably expected to increase in the near future.

Eliminate.

E. the population of Tennessee warblers is declining less sharply than the population of Baltimore orioles

No such comparative information is provided by the passage.

Eliminate.

Correct answer:   B

guddo · Answer

Migratory North American songbirds like the Tennessee warbler and the Baltimore oriole depend on the dense tree cover that has long been a feature of South American coffee plantations. This tree cover is being eliminated. Yet a population decline among Tennessee warblers is being attributed to a temporary drop in the population of spruce budworms, the warbler’s favorite North American prey. Baltimore orioles, however, do not eat budworms and are also experiencing a population decline.
 
 The information above, if accurate, could best serve as part of an argument that

The passage suggests that the Tennessee warbler’s decline may not be caused only by the temporary drop in spruce budworms. Baltimore orioles are also declining, even though they do not eat budworms.  That points to a shared cause , namely the loss of South American tree cover, which affects both birds during migration or wintering.

A. the decline in the numbers of the Tennessee warbler is responsible for the decline in the population of the spruce budworm

This reverses the suggested relationship. The passage says the budworm decline is being used to explain the warbler decline, not the other way around.

B. the Tennessee warbler population will not rebound when the spruce budworm population returns to normal

This is correct. If the warbler decline is at least partly caused by loss of tree cover, then the population may not recover simply because the budworm population returns to normal. The budworm drop may be only a  partial or mistaken explanation .

C. variations in the population of the Tennessee warbler influence the numbers of the Baltimore oriole

This is unsupported. The passage gives no reason to think one bird’s population affects the other’s.

D. the population of Tennessee warblers can reasonably be expected to increase in the near future

This is not supported. The passage gives a reason to doubt that the decline is only temporary.

E. the population of Tennessee warblers is declining less sharply than the population of Baltimore orioles

This is unsupported. The passage says both are declining but gives no comparison of how sharply.

Answer: (B)

minionbaba · Answer

The key is that the passage gives evidence that :    the spruce budworm explanation is incomplete or wrong.   
 Let's map it carefully. 
 Facts 
 
 Tennessee warblers depend on South American tree cover.  
 That tree cover is disappearing.  
 Tennessee warbler populations are declining.  
 Some people attribute the decline to a temporary drop in spruce budworms.  
 Baltimore orioles are also declining.  
 Baltimore orioles  do not eat budworms .  
 Orioles also depend on the same disappearing South American tree cover.

What does the oriole evidence suggest?

Since orioles don't eat budworms, their decline cannot be explained by budworm shortages.

So a more likely common cause of both declines is: Loss of South American tree cover

Now connect to B

If the real problem is disappearing tree cover, then:
 
 Budworms may eventually return to normal.  
 But the tree cover may still be gone.

Therefore: Even when budworms recover, Tennessee warblers may continue to struggle.

Which supports:
 (B) The Tennessee warbler population will not rebound when the spruce budworm population returns to normal.

Ambery · Answer

I don't think the answer should be B. It should be D. If B is correct, it implies that the premise "a population decline among Tennessee warblers is being attributed to a temporary drop in the population of spruce budworms" is wrong. However, we should not question premises in passage even in a weakening question. This question is a inference and the question stem itself "The information above, if accurate, could best serve as part of an argument that" is telling us that everything in passage is correct. I don't see why we should choose B. If it is accurate that "a population decline among Tennessee warblers is being attributed to a temporary drop in the population of spruce budworms", then when the budworm population returns to normal, the warbler population will rebound more or less for sure, although may not rebound to its original number due to the elimination of tree cover. So, I think B should be wrong. And since the budworm population drop is only temporary, we can say that "the population of Tennessee warblers can reasonably be expected to increase in the near future". So, D should be correct.

There is a similar weakening question: https://gmatclub.com/forum/kate-the-rec ... 25720.html. The answer choice A definitely weakens the hypothesis. If we apply the same logic of the weakening question to this inference one, it is understandable why B is correct. However, they are different questions and the inference question is not asking us to seriously call into question of a premise (which is not a hypothesis).

Can someone help to clear my above doubts? Thanks.

KarishmaB · Answer

We are looking for an inference here.

Premises:

Migratory NA songbirds like the warbler and the oriole depend on the dense tree cover of SA coffee plantations. 
This tree cover is being eliminated. 
Yet a population decline among warblers is being attributed to a temporary drop in the population of budworms, warbler’s food in NA. Orioles do not eat budworms and are also experiencing a population decline.

So the author tells us that warbler and oriole are migratory and depend on dense trees of SA. The tree cover is reducing. 
But decline in budworms is being claimed as the reason for decline in population or warblers. Orioles do not eat budworms but their numbers are also declining... So what is the author getting at? What could he be leading up to?

- Perhaps he wants to say that the reducing tree cover is the reason for reducing warblers, not budworms (or not only budworms). After all, both warblers and orioles are reducing in number though orioles do not get impacted by budworms. So the common thread here is the SA tree cover. So don't think that when budworm population recovers, warbler population will increase too. It may not because SA coffee plantation could be the bigger problem.

Look at the options:

A. the decline in the numbers of the Tennessee warbler is responsible for the decline in the population of the spruce budworm
  
No sense. Warblers are the predators. Decline in their number would improve the numbers of budworms.

B. the Tennessee warbler population will not rebound when the spruce budworm population returns to normal

Correct. As we discussed above.

C. variations in the population of the Tennessee warbler influence the numbers of the Baltimore oriole
  
The argument does not imply anywhere that numbers of warblers and orioles impact each other.

D. the population of Tennessee warblers can reasonably be expected to increase in the near future.
  
No. In fact, he seems to be driving the point that warbler population may not increase in near future.

E. the population of Tennessee warblers is declining less sharply than the population of Baltimore orioles
  
If anything, we can expect warbler population to decline more sharply than orioles because of budworm + coffee plantation impact.

Answer (B)

egmat · Answer

Hi Ambery,

You've read the question carefully, and you're right about one thing: we treat everything in the passage as accurate. But look closely at  what  the passage actually states as accurate.

The premise is not "the warbler decline  is caused by  a temporary budworm drop." It is:

"a population decline among Tennessee warblers  is being attributed to  a temporary drop in the population of spruce budworms."

That's a reported attribution, not an established fact.  What's accurate is that  people are blaming  the budworms - not that the budworms are the real cause. So choosing B doesn't reject any premise. It just declines to accept that the attribution is  correct .

And the passage hands you a strong reason to doubt that attribution: Baltimore orioles are  also  declining, yet they  don't eat budworms . Both birds share one thing - dependence on the tree cover that "is being eliminated." That points to habitat loss as the common cause. If the real driver is disappearing tree cover, then even when budworms return to normal, the warblers won't bounce back - exactly what  B  says.

This is also why the stem matters: "could best serve as part of an argument that" asks which conclusion the facts  support building toward  - and these facts build toward challenging the budworm story, not confirming it. That's why  D  fails: it assumes the budworm attribution is the whole truth, so the temporary drop means a rebound. The oriole evidence undercuts that assumption.

Turn one knob to feel it:

- If the passage said the decline " is caused by  a temporary budworm drop" - then yes, a rebound (D) would follow.
- But it says " is being attributed to " - a claim the oriole fact quietly undermines.

Watch that phrase "is being attributed to": it's the author reporting someone's explanation, not endorsing it.

Answer: B

Ambery · Answer

I got it now. Thank you!!!  egmat   KarishmaB

Migratory North American songbirds like the Tennessee warbler and the

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