Every fall Croton's jays migrate south. The jays always join flocks of

Wouldn't E indicate that CJs follow CB up north?

Before does not signify whether they are in the vision of CJ's to follow.

If they migrate a month before, CJ cannot see the CB, unless CB moves an inch a day.

if they migrate 10 min before, CJ possibly can see CB in the air and follow them for navigation.

Also the Q is clearly about moving together. not before/behind.

I narrowed it down to C and D, and picked C based on the assumption that the jays always need someone to migrate with, hence,

Conclusion: The jays can't navigate south on their own.
Evidence: Share migration with crookbeaks, if jay is lost :: jay finds crookbeaks
Assumption: The jays always migrate with birds of a differing species.

Not sure if this is entirely the correct reasoning...guess I would've been a little lucky.

Since I'm not a native speaker, I really can't understand the latter part in A "which breed upon completing their southern migration." what does this mean? Appreciated if anyone care to help!!

It means they reproduce after they have completed their journey. i.e have sex and give birth

So C seems to be the best available option!

Here's the explanation:

The conclusion of the given argument is that 'Croton's jays lack the navigational ability to find their way south on their own'. The question asks us to strengthen the argument and hence this conclusion. Which of the given options would prove that the Croton's jays, indeed lack the navigational ability to find their way (south, north or any other direction)?

Option C clearly supports our conclusion by stating that the Croton's jays migrate north in the company of Tattersall warblers and it has already been given in the premise that Croton's jays always join flocks of migrating crookbeaks to travel south. Hence this option, along with the given premise supports the conclusion that Croton's jays indeed lack the navigational ability to find their way.

The other four options are clearly out of scope of the given argument.

Hope this helps.

Every fall Croton's jays migrate south. The jays always join flocks of migrating crookbeaks with which they share the summer and winter territories. If a jay becomes separated from the crookbeaks it is accompanying, it wanders until it comes across another flock of crookbeaks. Clearly, therefore, Croton's jays lack the navigational ability to find their way south on their own.

Which of the following, if true, most strengthens the argument above?
A - Croton's jays lay their eggs in the nest of crookbeaks, which breed upon completing their southern migration.
B - The three species of most closely related to crookbeaks do not migrate at all.
C - In the spring, Croton's jays migrate north in the company of Tattersall warblers.
D - Species other than Croton's jays occasionally accompany flocks of migrating crookbeaks.
E - In the spring, crookbeaks migrate north before Croton's jays do.

What need to find = most strengthens the argument above

conclusion words ----clearly , therefore

Conclusion ----. Clearly, therefore, Croton's jays lack the navigational ability to find their way south on their own.

Need to emphasis on conclusion ----let's discuss each given statement


A - Croton's jays lay their eggs in the nest of crookbeaks, which breed upon completing their southern migration.

conclusion is on navigational ability to find the way in the argument , which needs to be strengthens ,while statement A emphasis on the habit of CJ laying eggs in the nest of crookbeaks


B - The three species of most closely related to crookbeaks do not migrate at all.

Premises is about only CJ and Crookbeaks , which are specific in the argument , while three species are general ---not related to argument


C - In the spring, Croton's jays migrate north in the company of Tattersall warblers.


migrate north in the company ------Croton's jays lack the navigational ability to find their way south on their own , means CJ Needs company to reach ----strength


D - Species other than Croton's jays occasionally accompany flocks of migrating crookbeaks.

Species other than Croton's-----out of scope , argument is about CJ

E - In the spring, crookbeaks migrate north before Croton's jays do.

look at word ---Before ---To strengthen we need together or accompany

Answer c

Option C never says about south and is not a good contender for answer. It does not give thought whether Jays cannot travel to south with out help.

Option E says Crookbeaks travel with out Jays, means Jays may or may not require some one to take them to North but they require some one to take to South.

Not able to understand how Option C is better than Option E.

Crotons (Lack the navigational ability) ---------follow ------> Crookbeaks

E. In the spring, crookbeaks migrate north before Croton's jays do.

If crookbeaks migrate before Crotons , we cannot state whether Croton will reach their destination/not, hence this doesn't strengthen the conclusion...

To strengthen the conclusion " Croton's jays lack the navigational ability to find their way south on their own." we need a statement to show that the Crotons are dependent on the crookbeaks for navigation/migration and only (C) does it perfectly.

To prove : Croton's jays lack the navigational ability to find their way south on their own.

As mentioned in the passage, Croton's jay is dependent on crookbeaks for migration to south.
If we are able to find some clue which suggests that the Croton's jay needs the same kind of help in migration, then that will help to strengthen the argument.
option (C) suggests the same.

Ans : C

Every fall Croton's jays migrate south. The jays always join flocks of migrating crookbeaks with which they share the same summer and winter territories. If a jay becomes separated from the crookbeaks it is accompanying, it wanders until it comes across another flock of crookbeaks. Clearly, therefore, Croton's jays lack the navigational ability to find their way south on their own.

Which of the following, if true, most strengthens the argument above?
A. Croton's jays lay their eggs in the nests of crookbeaks, which breed upon completing their southern migration.
Out of scope
B. The three species most closely related to crookbeaks do not migrate at all.
out of scope
C. In the spring, Croton's jays migrate north in the company of Tattersall warblers.
Correct choice that strenthens the conclusion of the argument that says that Croton's jays lack navigational ability.
D. Species other than Croton's jays occasionally accompany flocks of migrating crookbeaks.
Out of scope
E. In the spring, crookbeaks migrate north before Croton's jays do.
weakens the argument

(C) In the spring, Croton's jays migrate north in the company of Tattersall warblers.

I narrowed it down to (C) and (E) and chose E because "migrate north in the company" shows that the Crotons migrate together with another species, indicating they may not necessarily be able to navigate themselves.

(E) In the spring, crookbeaks migrate north before Croton's jays do.
Versus (E), I initially interpreted that the Crotons follow the Crookbeaks after they migrate, BUT that is a massive assumption as "migrate" is a synonym for journey. So if Crotons follow the Crookbeaks AFTER they migrate, then it means they are travelling alone and thus able to navigate. This is a 180 degree option. I.e. it Weakens the Conclusion.

Really, none of the answers here are good. This is a horrific question. I picked A because it seemed somewhat relatable to the fact that the CB's cannot migrate south on their own, and after reading it, I can see why A is out of scope, but still: it is asking about migrating south, therefore how does CB's going with someone in the north strengthen it? I can think of a million CR questions where I have seen these types of answer choices (i.e., conclusion asks for south and answer is north) and it is incorrect. This is bad by the GMAT -- is this how they're going to make us struggle for a high score?!

Totally agree, this is one of those questions where we have to mark the answer which feels the least wrong.
I marked (A) as well with the same reasoning, marking (C) is like using transitive property which doesn't really translate well in CR questions.

C gives another reason to beleive that they don't have navigational ability. Hence the answer

C is the most suitable answer. The fact that Croton's jays migrate north in the company of Tattersall warblers does support the argument that Croton's jays lack navigation ability and hence rely on other animals to guide them.

A ---> the nesting habits isnot relevant to the argument.
B ---> the argument relates to Croton's jay while this option mentions about species closely related to crookbeaks. Thus, not too relevant.
D ---> this is either irrelevant or weakens the argument that Croton's jay follows the crookbeaks for navigation.
E ---> this weakens the argument as it suggest that Croton's jay is independent of crookbeaks for directional purposes.


Every fall Croton's jays migrate south. The jays always join flocks of migrating crookbeaks with which they share the same summer and winter territories. If a jay becomes separated from the crookbeaks it is accompanying, it wanders until it comes across another flock of crookbeaks. Clearly, therefore, Croton's jays lack the navigational ability to find their way south on their own.

Which of the following, if true, most strengthens the argument above?


(A) Croton's jays lay their eggs in the nests of crookbeaks, which breed upon completing their southern migration.

(B) The three species most closely related to crookbeaks do not migrate at all.

(C) In the spring, Croton's jays migrate north in the company of Tattersall warblers.

(D) Species other than Croton's jays occasionally accompany flocks of migrating crookbeaks.

(E) In the spring, crookbeaks migrate north before Croton's jays do.

"...Clearly, therefore, Croton's jays lack the navigational ability to find their way south on their own."

I got really confused by 'south' part because it indicates that we are specifically talking about its ability to navigate south and not general navigational ability. Which is why eliminated C.

I marked A on the assumption that it reiterates that the jays travel south with or after crookbeaks