Three hypotheses have been proposed to account for the fact that, in many bird species, juveniles differ markedly from adults...
GMAT Reading Comprehension : (RC) Questions
Three hypotheses have been proposed to account for the fact that, in many bird species, juveniles differ markedly from adults in the feeding sites they use. The specialized diet hypothesis states that juveniles and adults have become specialized in using different food resources and choose their feeding site accordingly. The inefficient site evaluation hypothesis states that juveniles may choose less profitable feeding sites because they are less able than adults to evaluate site differences efficiently. The competition hypothesis states that juveniles are forced to use suboptimal feeding sites because of competition with adults.
In a study testing the competition hypothesis, researchers found that when a significant number of adults were removed from a particular pigeon population, juveniles increasingly used the feeding site that offered the greatest food availability; when the population recovered its initial size through the influx of adult pigeons from nearby populations, juveniles resumed more frequent use of suboptimal sites. These results support the competition hypothesis and contradict both the specialized diet and inefficient site evaluation hypotheses, neither of which would predict any behavioral response to the removal of individuals. The inefficient site evaluation hypothesis can be further discounted because pigeons forage in flocks and the pigeons studied live in small home ranges, both of which allow juveniles to quickly acquire knowledge of suitable foraging sites.
The fact that pigeons forage in flocks serves in the passage to
1. Passage Analysis:
Progressive Passage Analysis
| Text from Passage | Analysis |
|---|---|
| Three hypotheses have been proposed to account for the fact that, in many bird species, juveniles differ markedly from adults in the feeding sites they use. | What it says: Scientists have three different theories to explain why young birds and adult birds eat in different places. What it does: Sets up the main topic and tells us there are competing explanations Source/Type: Factual statement about scientific research Connection to Previous Sentences: This is our starting point - no previous information to connect to What We Know So Far: Young and adult birds feed in different places, and scientists have 3 theories about why What We Don't Know Yet: What the 3 theories are, which one is correct Visualization: Think of sparrow families where baby birds might eat near the nest while parents fly to distant fields Reading Strategy Insight: The author is being organized - promising to explain 3 theories. Expect structure, not chaos. |
| The specialized diet hypothesis states that juveniles and adults have become specialized in using different food resources and choose their feeding site accordingly. | What it says: Theory #1: Young birds and adult birds have evolved to eat different types of food, so they naturally go to different places to find their preferred food. What it does: Explains the first of the three theories Source/Type: Scientific hypothesis (researcher's theory) Connection to Previous Sentences: This directly delivers on the promise from sentence 1 - giving us the first of the three theories Visualization: Baby woodpeckers might eat soft insects from tree bark while adults eat hard nuts from tree tops Reading Strategy Insight: The author is systematically delivering what was promised. This reduces complexity by following a clear structure. |
| The inefficient site evaluation hypothesis states that juveniles may choose less profitable feeding sites because they are less able than adults to evaluate site differences efficiently. | What it says: Theory #2: Young birds aren't good at figuring out which feeding spots are best, so they end up in worse locations than adults. What it does: Explains the second theory Source/Type: Scientific hypothesis (researcher's theory) Connection to Previous Sentences: This continues the systematic explanation started in sentence 1, giving us theory #2 of 3 Visualization: Like inexperienced shoppers who go to expensive stores while experienced shoppers find the best deals Reading Strategy Insight: Still following the promised structure. We're 2/3 of the way through the theories - complexity is organized, not random. |
| The competition hypothesis states that juveniles are forced to use suboptimal feeding sites because of competition with adults. | What it says: Theory #3: Adult birds push young birds out of the good feeding spots, forcing young birds to use worse locations. What it does: Explains the third and final theory Source/Type: Scientific hypothesis (researcher's theory) Connection to Previous Sentences: This completes the set of three theories promised in sentence 1 What We Know So Far: All 3 competing theories about why young and adult birds feed in different places What We Don't Know Yet: Which theory is correct, what evidence exists Visualization: Like adult customers getting the best restaurant tables while families with kids get seated in noisy sections Reading Strategy Insight: Feel relieved here - the author delivered exactly what was promised. No surprises, just organized explanation. |
| In a study testing the competition hypothesis, researchers found that when a significant number of adults were removed from a particular pigeon population, juveniles increasingly used the feeding site that offered the greatest food availability; when the population recovered its initial size through the influx of adult pigeons from nearby populations, juveniles resumed more frequent use of suboptimal sites. | What it says: Scientists tested theory #3 (competition) with pigeons. When they removed adult pigeons, young pigeons started using the best feeding spots. When adults came back, young pigeons went back to worse spots. What it does: Provides concrete evidence to test one of the three theories Source/Type: Research findings (experimental data) Connection to Previous Sentences: This moves from theory (sentences 2-4) to testing (sentence 5). The author is now providing evidence for one specific theory. Visualization: Experiment Phase 1: 100 adult pigeons + 50 young pigeons → young pigeons feed in poor areas Experiment Phase 2: 50 adult pigeons removed → young pigeons move to best feeding areas Experiment Phase 3: 100 adult pigeons return → young pigeons pushed back to poor areas Reading Strategy Insight: The passage is moving logically from 'here are the theories' to 'here's evidence.' This is building understanding, not adding confusion. |
| These results support the competition hypothesis and contradict both the specialized diet and inefficient site evaluation hypotheses, neither of which would predict any behavioral response to the removal of individuals. | What it says: The pigeon experiment proves theory #3 (competition) is correct and proves theories #1 and #2 are wrong. What it does: Provides the conclusion from the evidence and eliminates competing theories Source/Type: Author's interpretation of research results Connection to Previous Sentences: This is the payoff! This directly answers the question set up in sentence 1 - which of the 3 theories is correct. What We Know So Far: Competition theory is correct; the other two theories are wrong Visualization: ✓ Theory #3 (Competition): SUPPORTED by evidence ✗ Theory #1 (Specialized diet): CONTRADICTED ✗ Theory #2 (Inefficient evaluation): CONTRADICTED Reading Strategy Insight: This is simplification, not new complexity! The author just eliminated 2 of 3 theories, making the answer clearer. |
| The inefficient site evaluation hypothesis can be further discounted because pigeons forage in flocks and the pigeons studied live in small home ranges, both of which allow juveniles to quickly acquire knowledge of suitable foraging sites. | What it says: Theory #2 (inefficient evaluation) is definitely wrong because young pigeons learn quickly by watching others and don't need to travel far. What it does: Provides additional evidence against one of the rejected theories Source/Type: Author's reasoning based on pigeon behavior facts Connection to Previous Sentences: This REINFORCES the conclusion from sentence 6. The author is making sure we understand why theory #2 doesn't work. Visualization: Young pigeons in a flock of 20 birds in a 2-block neighborhood can easily learn where the best food is by watching experienced birds Reading Strategy Insight: This is the author being helpful, not adding complexity. They're giving us extra reasons to be confident in rejecting theory #2. Feel more certain, not more confused! |
2. Passage Summary:
Author's Purpose:
To evaluate three competing scientific theories about why young and adult birds feed in different places by presenting experimental evidence that supports one theory and rules out the others.
Summary of Passage Structure:
The author builds their argument in clear steps:
- First, they introduce the puzzle that scientists are trying to solve - why young birds and adult birds use different feeding spots
- Next, they systematically present all three theories that scientists have proposed to explain this behavior
- Then, they describe a controlled experiment with pigeons that tested one of these theories by removing adult birds and observing what happened
- Finally, they explain how the experimental results prove one theory correct while disproving the other two, and provide additional reasoning to further strengthen their conclusion
Main Point:
The competition theory is correct - young birds use worse feeding spots because adult birds push them out of the best locations, not because young birds prefer different food or are bad at finding good spots.
3. Question Analysis:
The question asks us to identify the specific role that "the fact that pigeons forage in flocks" plays in the author's argument. This is asking about a particular detail's function within the broader passage structure.
Connecting to Our Passage Analysis:
From our passage analysis, we can see that the mention of flocking behavior appears in the final sentence, which provides "additional evidence against one of the rejected theories." Specifically, our analysis showed:
- The passage systematically presents three competing theories about juvenile vs. adult feeding behavior
- Experimental evidence supports the competition hypothesis while contradicting the other two
- The final sentence provides "extra reasons to be confident in rejecting theory #2" (the inefficient site evaluation hypothesis)
- The flocking behavior is presented as one of two factors that "allow juveniles to quickly acquire knowledge of suitable foraging sites"
Prethinking:
Based on our understanding that the passage moves from presenting theories → testing theories → concluding which theory is correct → providing additional evidence to strengthen that conclusion, the flocking behavior must serve to further discredit the inefficient site evaluation hypothesis. If young pigeons can learn quickly by observing others in flocks, then they wouldn't be "inefficient" at evaluating feeding sites, which undermines that entire theory.
Why It's Wrong:
- The flocking behavior is mentioned to discredit the inefficient site evaluation hypothesis, not support the specialized diet hypothesis
- The passage already established through experimental evidence that the competition hypothesis (not specialized diet) is correct
- Nothing in the discussion of flocking relates to different food preferences or specialized diets
Common Student Mistakes:
- Did I confuse which hypothesis the passage supports?
→ Remember: the experimental evidence supports the competition hypothesis, and flocking behavior is used to further reject a different hypothesis - Am I mixing up the three different theories?
→ Specialized diet = different food preferences; inefficient evaluation = poor judgment; competition = adults push out juveniles
Why It's Wrong:
- The passage discusses flocking in relation to juvenile learning, not adult behavior specifically
- The focus is on how flocking helps juveniles "quickly acquire knowledge," which relates to the inefficient site evaluation hypothesis
- The passage doesn't use flocking behavior to explain any particular aspect of what adults do
Common Student Mistakes:
- Did I focus on "adults" because the passage mentions adult-juvenile competition?
→ The flocking discussion specifically addresses juvenile learning ability, not adult behavior patterns
Why It's Right:
- The passage explicitly states this hypothesis "can be further discounted" because of flocking behavior
- Flocking allows juveniles to "quickly acquire knowledge of suitable foraging sites," which directly contradicts the idea that juveniles are inefficient at site evaluation
- This appears in the final sentence as additional evidence to strengthen the rejection of this hypothesis
Key Evidence: "The inefficient site evaluation hypothesis can be further discounted because pigeons forage in flocks and the pigeons studied live in small home ranges, both of which allow juveniles to quickly acquire knowledge of suitable foraging sites."
Why It's Wrong:
- Flocking behavior is used to support the conclusion, not raise objections to it
- The experimental evidence already strongly supports the competition hypothesis
- The flocking discussion reinforces the overall argument by eliminating a competing theory
Common Student Mistakes:
- Am I thinking that since flocking could help juveniles compete, it might contradict the competition hypothesis?
→ The flocking evidence targets the inefficient evaluation hypothesis specifically, not the competition hypothesis
Why It's Wrong:
- Small home ranges and flocking are presented as two separate factors that both contribute to juvenile learning
- The passage doesn't suggest that flocking causes small home ranges or vice versa
- Both factors are used together to explain why juveniles can learn quickly, undermining the inefficient evaluation theory
Common Student Mistakes:
- Did I assume the two factors mentioned together must be causally related?
→ The passage presents them as independent factors that both contribute to the same outcome (quick learning)