Q5 - The population of songbirds throughout

[peg_city]

Why is b wrong?

If the number of eggs laid yearly from a female songbird varies widely then couldn't that be the reason behind the decrease in population in recent years?

And Why is C right?

Thanks ahead of time

[giladedelman]

Thanks for posting!

So, we're trying to weaken the argument that the decline in the songbird population is due to the increase in the magpie population.

(C) weakens this argument because if those areas in which the songbird population decreased didn't experience any growth in the magpie population, then the decrease must have been caused by something other than magpie population growth -- no such growth occurred there!

(Imagine I argued that the increase in car accidents in the U.S. is due to the increase in red cars, which are known to be involved in more accidents. But what if it turned out that in those parts of the country where there were more accidents, there were no more red cars than before? Would it make sense to blame the red cars anymore?)

As for (B), two things. First, be careful not to misread it. It says that the number of eggs laid yearly varies according to species. In other words, different songbird species lay different numbers of eggs. That's different from saying that a particular songbird lays a different number each year. Now, the argument tells us that the overall songbird population has decreased. So the fact that different species lay different numbers of eggs doesn't help us determine this overall decline.

Second thing: even if answer (B) said what you thought it did, it still wouldn't help us. The fact that a songbird might lay different numbers of eggs each year doesn't tell us one way or the other whether magpies were responsible for the songbird decline. In other words, just because the egg number might vary, that doesn't tell us whether the population should increase or decrease.

Does that clear this one up for you?

[peg_city]

Thanks for posting!

So, we're trying to weaken the argument that the decline in the songbird population is due to the increase in the magpie population.

(C) weakens this argument because if those areas in which the songbird population decreased didn't experience any growth in the magpie population, then the decrease must have been caused by something other than magpie population growth -- no such growth occurred there!

(Imagine I argued that the increase in car accidents in the U.S. is due to the increase in red cars, which are known to be involved in more accidents. But what if it turned out that in those parts of the country where there were more accidents, there were no more red cars than before? Would it make sense to blame the red cars anymore?)

As for (B), two things. First, be careful not to misread it. It says that the number of eggs laid yearly varies according to species. In other words, different songbird species lay different numbers of eggs. That's different from saying that a particular songbird lays a different number each year. Now, the argument tells us that the overall songbird population has decreased. So the fact that different species lay different numbers of eggs doesn't help us determine this overall decline.

Second thing: even if answer (B) said what you thought it did, it still wouldn't help us. The fact that a songbird might lay different numbers of eggs each year doesn't tell us one way or the other whether magpies were responsible for the songbird decline. In other words, just because the egg number might vary, that doesn't tell us whether the population should increase or decrease.

Does that clear this one up for you?

Yes

Thank you

[WaltGrace1983]

I'll add the wrong ones!

(A) We don't care about how long the official records have been kept. We are only talking about "recent years" anyway! No need to go back 30 years!

(D) We don't care why the population of magpies has increased. We ONLY care about why the population of songbirds has decreased.

(E) We don't care about the other stuff magpies eat. We need to find out what caused/didn't cause the songbird's decrease in population!