Logical Reasoning

PT16 · S2 · Q5 The population of songbirds

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The population of songbirds throughout England has decreased in recent years.

Curious Fact

Why has the population of songbirds in England gone down in recent years?

Explanation

There has been an increase during the same period in the population of magpies. Magpies eat the eggs and chicks of songbirds.

Evaluate

To weaken this argument, we could suggest alternate explanations for the decline of songbirds, such as other environmental factors or threats. Alternatively, we could attack the plausibility that an increase in magpies directly leads to a decrease in songbirds by pointing out situations in which the rise in magpies does not correlate with a decline in songbirds.

Goal

Let's find an answer that provides an alternate explanation for why songbirds are decreasing in England, or one that debunks the story that an increase in magpies is negatively affecting songbirds.

Which one of the following, if true, argues most strongly against the explanation reported in the passage?

Official records of the population
No Impact
While the duration of official records may matter for long-term trends, it doesn't impact the explanation regarding magpies affecting songbirds' recent decline. The argument doesn't rely on the historical depth of records but on the correlation between recent increases in magpies and decreases in songbirds.
1% picked this
The number of eggs laid
Unclear Impact
The variation among different species of songbirds in their egg production doesn't directly affect the argument about magpies being the reason for the decline. In recent years, has songbird egg production been higher or lower in England? And what does the rate of egg production have to do with whether or not magpies are a causal factor?
9% picked this
Correct
Although the overall population of
Why this is right
This impugns the plausibility of the author's hypothesis that an increase in magpies is causing a decrease in songbirds. The answer has the classic Effect w/o Cause form. There are places where we observe a decrease in songbirds, even though we don't have an increase in magpies. That suggests that something besides "more magpies" is apparently causing the songbird decreases in most areas.
Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.
75% picked this
The population of magpies has
No Impact
While this gives a reason for the magpie population increase, it doesn't directly argue against the magpie effect on songbirds. Understanding why magpies increased doesn’t necessarily impact whether magpies are causing a reduction in songbird populations.
6% picked this
Although magpies eat the eggs
No Impact
Magpies can have varied diets, but this doesn't weaken the causal link that their predation on songbird eggs and chicks could still impact songbird populations. Eating other foods doesn't mean they can't still negatively impact songbird populations through predation. We can't say, "it's plausible that an increase in magpies could lead to a decrease in songbirds, since songbird eggs aren't the only thing that magpies eat."
9% picked this

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