Guillemots are birds of Arctic regions. They feed on fish that gather

I understand (D) perfectly. But can someone please explain why fish under the ice will disappear because of melting ice?


We have to assume that fish needs ice in order to survive. But that's just another assumption.

Hey All,

Enough questions enough that I figured it might be worth my weighing in. As any good instructor would, I'm going to focus on the passage first.

Conclusion: Warming will extend Guillemots range north

Premises: Guillemots feed on fish beneath ice, nesting nearby. Need snow-free area to raise chicks. Area is warming, particularly north.

Assumption: Something other than the warming will keep them from extending range.

We know the assumption will be this limited, because otherwise the argument is solid (i.e. if the warm area is expanding, and they can live in warm weather, then obviously their range will expand).

(A) Even if the warming trend continues, there will still be years in which guillemot chicks are killed by an unusually early snow.
Problem: This has no connection to the issue of range, because this would happen anywhere.

(B) If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.
Problem: In a number of answer choices here, the question is trying to trick you into thinking that the conclusion is that the guillemots will THRIVE in the new areas. But that's not the conclusion. The conclusion is merely that the range of areas in which they can survive will expand. This has no effect on that. The same predators joining them in the new area will result in much the same lifestyle the guillemots already have (same predators).

(C) Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.
Problem: This doesn't affect the conclusion, which is that the increasing temperatures ELSEWHERE will expand the range of the guillemots.

(D) If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.
Answer: This one may look out of scope, but remember that scope isn't really an issue on strengthen/weaken questions; you're allowed to bring in other information. If the thin ice disappears, then the guillemots will not be able to expand their habitat, because they survive on the fish that live under the ice. This relates to their ability to expand. To contrast with B, the predators are THE SAME in the new area or the old. In D, the food source is DIFFERENT (worse) in the new area, which weakens the conclusion.


(E) The fish that guillemots eat are currently preyed on by a wider variety of predators in the southernmost Arctic regions than they are farther north.
Problem: This actually strengthens the argument, because the guillemots are planning to move north. fewer predators means a better chance of succeeding.

Hope that helps!

(B) If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.

D) If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.

(E) The fish that guillemots eat are currently preyed on by a wider variety of predators in the southernmost Arctic regions than they are farther north.

The author thinks that the rise in temperatures will cause the birds' range to be extended northward along the coast.

Hey All,

Enough questions enough that I figured it might be worth my weighing in. As any good instructor would, I'm going to focus on the passage first.

Conclusion: Warming will extend Guillemots range north

Premises: Guillemots feed on fish beneath ice, nesting nearby. Need snow-free area to raise chicks. Area is warming, particularly north.

Assumption: Something other than the warming will keep them from extending range.

We know the assumption will be this limited, because otherwise the argument is solid (i.e. if the warm area is expanding, and they can live in warm weather, then obviously their range will expand).

(A) Even if the warming trend continues, there will still be years in which guillemot chicks are killed by an unusually early snow.
Problem: This has no connection to the issue of range, because this would happen anywhere.

(B) If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.
Problem: In a number of answer choices here, the question is trying to trick you into thinking that the conclusion is that the guillemots will THRIVE in the new areas. But that's not the conclusion. The conclusion is merely that the range of areas in which they can survive will expand. This has no effect on that. The same predators joining them in the new area will result in much the same lifestyle the guillemots already have (same predators).

(C) Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.
Problem: This doesn't affect the conclusion, which is that the increasing temperatures ELSEWHERE will expand the range of the guillemots.

(D) If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.
Answer: This one may look out of scope, but remember that scope isn't really an issue on strengthen/weaken questions; you're allowed to bring in other information. If the thin ice disappears, then the guillemots will not be able to expand their habitat, because they survive on the fish that live under the ice. This relates to their ability to expand. To contrast with B, the predators are THE SAME in the new area or the old. In D, the food source is DIFFERENT (worse) in the new area, which weakens the conclusion.


(E) The fish that guillemots eat are currently preyed on by a wider variety of predators in the southernmost Arctic regions than they are farther north.
Problem: This actually strengthens the argument, because the guillemots are planning to move north. fewer predators means a better chance of succeeding.

Hope that helps!

VeritasKarishma AndrewN

B. If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.

C. Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.

D. If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.

I'd picked option B through my pre-thinking and after reading the above posts I see how B cannot weaken the argument (the birds need not thrive in the new regions, they may be equally under threat in the new northern regions), however, I'd made some assumptions about option C which made me think that it was a contender as well. Please confirm if this thought is logical -

Since Guillemots nest in coastal areas, and their primary food source is the fish under thin ice then they would continue to be restricted to that part of the arctic and not move inward into farther northern regions. Meaning that coastal birds would always continue to inhabit coastal regions, irrespective of whether the temperatures are higher there. Is my assumption that "northward" in Arctic terms means more "landlocked" and thereby unsuitable for coastal birds, incorrect?

Thanks for your help !

VeritasKarishma AndrewN

B. If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.

C. Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.

D. If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.

I'd picked option B through my pre-thinking and after reading the above posts I see how B cannot weaken the argument (the birds need not thrive in the new regions, they may be equally under threat in the new northern regions), however, I'd made some assumptions about option C which made me think that it was a contender as well. Please confirm if this thought is logical -

Since Guillemots nest in coastal areas, and their primary food source is the fish under thin ice then they would continue to be restricted to that part of the arctic and not move inward into farther northern regions. Meaning that coastal birds would always continue to inhabit coastal regions, irrespective of whether the temperatures are higher there. Is my assumption that "northward" in Arctic terms means more "landlocked" and thereby unsuitable for coastal birds, incorrect?

Thanks for your help !

So poor GMATNinjaTwo lives in New Jersey, where he's suffered through something called a "bomb cyclone" that caused sub-zero (Fahrenheit!) temperatures. He says that he saw a guillemot in his own backyard last week, but that sighting hasn't been verified. And he recommends this two-minute video about guillemot chicks: https://video.nationalgeographic.com/video/guillemots.

Anyway, back to the GMAT... the conclusion of the argument is that the guillemots’ range will probably be enlarged by being extended northward along the coast IF the warming in the Arctic continues. How does the author arrive at this conclusion?

• We are told that guillemots reside in Arctic regions and feed on fish that gather beneath thin sheets of floating ice.
• The birds nest on land near the floating ice.
• The birds need 80 consecutive snow-free days in a year to raise their chicks. Until recently, this fact limited the birds' range to the southernmost Arctic coast.
• However, average temperatures in the Arctic have begun to rise.
• The author thinks that the rise in temperatures will cause the birds' range to be extended northward along the coast. This might make sense... we can infer that it gets colder as you head north, so at some point along the coast there's a limit beyond which it is too cold/snowy for the birds' to raise chicks. If it starts to get warmer in general, that limit might be pushed northward.

Now we need an answer choice that would WEAKEN this logic:


An unusually early snow could happen even along the southernmost coast of the Arctic. As long as this is an unusual occurrence and not a regular occurrence, it would not prevent the guillemot's from moving northward. Sure, it would cause some bad years for the guillemots, but that would be true regardless of where they are living (i.e. regardless of how far north they live). Eliminate (A).


Choice (B) is tempting, but make sure you notice the word "current". The guillemots already have predators in the south. That doesn't PREVENT the guillemots from living in the south; it simply provides a challenge that the guillemots have to deal with.

If there were FEWER predators farther north, that would certainly make it easier for the guillemots. But if the guillemots' current predators simply move north as well, then the guillemots will face the same danger that they did in the south. Again, this wouldn't PREVENT the guillemots from living in the north; instead, it would mean they have to deal with the same predators that they deal with in the south.

Choice (B) can be eliminated.


This fact has no bearing on the author's argument. Will the rising temperatures allow the guillemots to expand their range? Choice (C) provides no evidence either way and can be eliminated.


The point of the argument is that "the guillemots’ range will probably be enlarged." We're not concerned with decreasing the number of guillemots, only the size of their range. The author's reasoning is that their range will expand as the bird moves northward.

The author assumes that the bird will only add to its range as it moves northward. Choice (D) suggests that the northward expansion will come with a decrease in the range along the southern coast (if the thin ice disappears, the fish that gather under the thin ice might have to move northward). Although this doesn't necessarily disprove the author's point, it's seriously weakens the argument. Hang on to this one.


Choice (E) suggests that the guillemots would have LESS competition for food as they move northward. This is evidence that the guillemots WILL be able to survive as they move in that direction. If instead choice (E) said the opposite (that the fish are preyed on by a wider variety of predators farther north), then it would weaken the argument. As is, choice (E) strengthens the argument and can be eliminated.

(D) is the best answer.

GMATNinja GMATNinjaTwo VeritasKarishma

Why can't we say from option C that, the birds anyways prefer high temperatures due to which they need not migrate northward and extend their range. Does this not hurt the author's argument? Also, in the premise it was mentioned that the birds need 80 snowy free days. Why do they need to extend their range at all?

(C) Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.

(B) If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.
Problem: In a number of answer choices here, the question is trying to trick you into thinking that the conclusion is that the guillemots will THRIVE in the new areas. But that's not the conclusion. The conclusion is merely that the range of areas in which they can survive will expand. This has no effect on that. The same predators joining them in the new area will result in much the same lifestyle the guillemots already have (same predators).