CR Practice - 2 (Cow birds)

Question

I dont like this one question...let me have your explanation and feedback on this question..
The red-eyed cowbird breeds by parasitizing the nests of orioles, among other birds. The cowbird lays its eggs in the orioles' nests while the female orioles are out searching for food. The cowbird has evolved certain traits and behaviors to ensure the success of its deception: It throws one oriole egg out of the nest for every one of its own eggs that it lays therein, and it has evolved an egg coloration similar to that of the oriole. An oriole whose nest has thus been parasitized will subsequently incubate and rear the cowbird chick, unaware of the cowbird's ploy. 

Which of the following conclusions can most properly be drawn from the information above?


A. The stability of oriole populations is threatened by the behavior of red-eyed cowbirds. 
B. The oriole does not possess any numeric ability. 
C. The stability of red-eyed cowbird populations depends on the proximity of nesting orioles. 
D. The red-eyed cowbird's behavior is not learned. 
E. Scientists are unable to distinguish between a red-eyed cowbird egg and an oriole egg based solely on visual examination

gayathri · Answer

Pick C

A: Possible, but I think it is little extreme. No where in paragraph does it refer to Oriole population declining...
B: Its counter to statement given. If the orioles cannot count, there is no reason for the cowbird to throw one oriole egg out of the nest for every one of its own eggs.
C: since cowbirds are parasitic, they rely on orioles for breeding. So, dueing breeding they need to be near Oriole nesting grounds
D: Cowbird has learned to do certain things like throw out an egg
E: No mention of scientists in the statement, only the orioles are unable to distinguish the egdd.

ruhi · Answer

Well, I dont seem to agree with any of the answer choices... A parasite is a being that lives on another being for food, benefits etc... But the definition does not include the fact that the other being on which the former becomes dependent should be present in close proximity.. its only later that the proximity develops.. So, I dont think its necessary that the cowbirds need to find an oriole nearby.. they can always travel great lengths... Secondly, Oriole is not the only bird it relies on.. The argument mentions it cleary that it is one of the birds on whom the cowbird relies... Have a look at this link.. It explains the meaning of a parasite... taken from various dictionaries... https://hyperdictionary.com/search.aspx?define=parasite

ninomoi · Answer

I kinda of agree with Ruhi - none of the choices really answers this one. However out of all of them I feel C is the best choice, even though A could come a close second. OOPS :oops:

On second thoughts it could just be A. C not sure cos it is said in the passage that the cowbirds do not only invade oriole nests but other nests as well. So that kinda rules C out for me. B - The oriole's numeracy skills should not come into play as the number of eggs will probably remain the same. D- Out of the scope of this passage I think. E - If this choice had said orioles instead of scientists I may have gone with this choice. What is d OA?

NEWKID · Answer

I will go with A.
And here is my attempt to explain why A.

Let there be N eggs laid by Oriloe. Cowbird has N eggs or more than N eggs. It come to Oriloe's nest when the female orioles are out searching for food. The cowbird will throw one oriole egg out of the nest for every one of its own eggs that it lays . So, it will remove N eggs of Oriole and replace them.
(Of course this explanation has a few assumptions. )
So, if this situation continues, there will fewer number of Oriole eggs.
Hence my vote for A.

forumsmba · Answer

I would go with C.

I don't think it's A because, even though NewKid's explanation about N eggs is correct, we actually don't have an information about how many is N. Oriloe might lay 10 eggs at a time and the cowbird might only lay 1 egg at a time. Since, this information is not given, I doubt if we can comment on the stability of Oriloe's population.

Given the explanation, I believe that Cowbirds exist only where Oriloe's exist. Hence, C.

-fm

foraj · Answer

Go with C, as stated in the argument that cowbirds cannot breed in any other way except using orioles nest.

ninomoi · Answer

Foraj, passage does say cowbirds breed using other birds' nests.

doggita · Answer

I feel C is the best choice here.

Paul · Answer

I agree with C as best although I don't like the "stability" of cowbird population depending on oriole proximity. What if the oriole represent only 1% of other bird eggs being parasitized? A is well refuted by forumsmba. Once again, C is best but it can also be refuted because it is based on the unwarranted assumption that oriole bird eggs account for the largest population that cowbird breeds parasitize.

venksune · Answer

Its not C as the cowbirds are not dependent on the Orioles alone - they do it with any other bird too. Surprisingly the OA is D.

I chose E and my logic was that, if the scientists can get fooled, a bird will also be fooled and will not know that it is not its egg. I never even shortlisted D. But D?!!

Here's the OE:
Given the fact that cowbird chicks are incubated and reared exclusively by non-cowbirds, their breeding behavior must be innate rather than learned, since they have no cowbird models after which to pattern themselves. Choice (A) is incorrect. While the passage does suggest that the oriole population decreases due to the cowbird's behavior, the author does not state or imply the extent to which the overall stability of the oriole population is affected. The oriole population may very well remain stable after factoring in a certain amount of loss due to the cowbird's switching tactic. The author suggests the opposite of choice (B), given that the cowbird purposely deletes one oriole egg from the nest for every cowbird egg it deposits. The fact that this evolved behavior is intended to deceive the oriole suggests that the oriole would notice if eggs were missing, implying at least a rudimentary numeric ability. Choice (C) is incorrect because the author states that the oriole is only one of several species that the cowbird parasitizes. Choice (E) is incorrect because what fools an oriole need not necessarily fool a scientist

ninomoi · Answer

Where did u get this question from, venksune? I would have never chosen D :!:

Paul · Answer

Interesting and very tricky question 8-)

ruhi · Answer

I think D makes perfect sense. I always always had doubts regarding C (as mentioned in the earlier post). None of the other choices come close.

praveen_rao7 · Answer

I am late on this. D is the answer
Following expression 
"The cowbird has evolved certain traits and behaviors to ensure the success of its deception" indicates that the behaviour is evolved/inherited as opposed to being learned. Hence D it is

CR Practice - 2 (Cow birds)

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