Our conclusion is: "learning how to build a nest plays an important part in the breeding success of birds."
Why? Because studies have shown that birds nesting for the first time are less successful in breeding than are older birds and less successful than they are themselves a year later.
Just because there is a correlation to years of nesting experience and breeding success does not mean that the years of nesting experience causes more and more success. It could be that something else caused the success.
Answer choice (B) addresses just this issue: "The capacity of blackbirds to lay viable eggs increases with each successive trial during the first few years of reproduction."
Here, answer choice (B) explains that it is in fact the age of a blackbird that contributes to more success in breeding since the capacity of blackbirds to lay viable eggs increases with each successive trial during the first few years of reproduction, as opposed to nesting experience being the cause of breeding success.
Thus, answer choice (B) successfully weakens the conclusion of the argument.
Hope that clears things up! Please let us know if you have any other questions.
YivillarFebruary 22, 2015
Thank you for the explanation
rmkrutz@crimson.ua.eduFebruary 24, 2018
Could you please explain how we would eliminate answer choice C?
MehranFebruary 28, 2018
The problem with (C) is that it doesn't weaken the conclusion.
This is a cause and effect argument. The authors proposed cause to the observed effect (i.e. that birds nesting for the first time are less successful in breeding than are older birds and less successful than they are themselves a year later) is "learning how to build a nest."
Notice (C) does not provide any new information. The question is WHY are birds less successful the first time.
Is it learning how to build a nest or something else?
So (C) has no impact on this argument and it would be eliminated.
Hope that helps! Please let us know if you have any other questions.
KellanNovember 26, 2018
Mehran,
In the question stem it states, "He finds that birds nesting for the first time are less successful in breeding......and also less successful a year later".
Answer (C) The breeding success of birds nesting for the second time is greater than that of birds nesting for the first time.
One is stating "less successful a second time (2nd year)" - Dr. Snow. And (C) is stating, "second time is greater".
How is C wrong?
RaviDecember 21, 2018
@Kellan,
It sounds like you may have misread the stimulus. In the stimulus, Dr. Snow finds that birds nesting for the first time are less successful in breeding than are older birds, and also less successful than they themselves are a year later. What this means is that not only are first-time nesting birds less successful than older birds, but they're also successful than they are the following year.
An easy analogy to think of is a rookie basketball player in the NBA. The equivalent of what Dr. Snow is saying is that the rookie isn't as good as veteran players, nor is he as good as he is as a second-year pro.
Dr. Snow's findings are used to support the conclusion that nesting experience matters for the breeding success of birds.
Answer C does not weaken the argument; in fact, it strengthens it. C basically doubles down on Dr. Snow's findings, as it says that the breeding success of birds nesting for the second time is greater than that of birds nesting for the first time.
Answer B weakens the argument because if the capacity of blackbirds to lay viable eggs increases with age, then that would provide an alternative explanation for the observation that the breeding success of blackbirds increases as they get older. This alternative cause does not support the argument's conclusion that experience in nest building is the reason for blackbirds' increased breeding success with age.
