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For bird species in which females are the sole incubators, a male can increase the female's percentage of time spent on the nest (nest attentiveness) by feeding the incubating female on the nest (incubation feeding). Given the benefits of nest attentiveness and the potential ability of incubation feeding to increase attentiveness, the question arises of why species vary in their rate of incubation feeding. One hypothesis suggests that greater incubation feeding is required in harsher microclimates because there the cost of leaving eggs unattended is greater. Under this hypothesis, nest attentiveness and incubation feeding rates should be highest in species using nest sites that are exposed to extreme temperatures that can threaten embryo development or survival. An alternative hypothesis is that incubation feeding is constrained by nest predation; increased trips to the nest are hypothesized to attract the attention of predators. Females can consume more food in one foraging trip off the nest than a male can bring back to the nest in one trip, so the number of trips to the nest can be reduced by females obtaining most of their own food. Therefore, under the nest predation hypothesis, species with a higher risk of nest predation should show increased foraging by females and lower rates of incubation feeding by males.
The nest predation hypothesis implies that in situations where there is a high risk of nest predation, which of the following statements regarding the behavior of nesting birds is most likely to be true?
| Text from Passage | Analysis |
|---|---|
| For bird species in which females are the sole incubators, a male can increase the female's percentage of time spent on the nest (nest attentiveness) by feeding the incubating female on the nest (incubation feeding). | What it says: In some bird species, only females sit on eggs to keep them warm. When males bring food directly to the female while she's sitting on the nest, she can spend more time on the nest. What it does: Establishes basic background information and key terms Source/Type: Scientific fact/established knowledge Connection to Previous Sentences: This is our starting point - no previous information to connect to Visualization: Imagine a female robin sitting on her nest. Without male feeding: she sits for 6 hours, then leaves for 2 hours to find food. With male feeding: she sits for 7.5 hours, only leaves for 30 minutes. Reading Strategy Insight: The author helpfully defines technical terms immediately (nest attentiveness = time spent on nest). This is setup, not complexity. What We Know So Far: Males can help females stay on nests longer by bringing food What We Don't Know Yet: Why some species do this more than others |
| Given the benefits of nest attentiveness and the potential ability of incubation feeding to increase attentiveness, the question arises of why species vary in their rate of incubation feeding. | What it says: Since staying on the nest is good, and male feeding helps females stay on the nest, why do some bird species have males that feed females more often than others? What it does: Poses the central research question Source/Type: Author framing the scientific inquiry Connection to Previous Sentences: This builds directly on sentence 1 by asking the logical follow-up question. Sentence 1 said "males CAN increase nest time through feeding" - now we ask "so why don't ALL species do this equally?" Visualization: Species A: Males bring food 10 times per day Species B: Males bring food 3 times per day Species C: Males bring food 1 time per day Question: Why these differences? Reading Strategy Insight: Feel confident here - this is just restating sentence 1 in question form. The author is helping by clearly stating what puzzle we're trying to solve. What We Know So Far: Males feeding females is beneficial, but species vary in how much they do it What We Don't Know Yet: What causes these variations |
| One hypothesis suggests that greater incubation feeding is required in harsher microclimates because there the cost of leaving eggs unattended is greater. | What it says: First possible answer: In places with extreme weather, males need to bring more food because it's more dangerous to leave eggs alone. What it does: Introduces the first hypothesis (harsh climate theory) Source/Type: Scientific hypothesis/researcher's theory Connection to Previous Sentences: This directly answers the question posed in sentence 2. We asked "why do feeding rates vary?" - here's potential answer #1. Visualization: Harsh climate area (desert): Eggs die in 30 minutes if left alone → Males bring food 8 times/day Mild climate area (forest): Eggs survive 2 hours alone → Males bring food 2 times/day Reading Strategy Insight: This follows classic RC pattern: pose question, then give possible answers. We're building understanding, not adding confusion. What We Know So Far: Hypothesis 1 says harsh weather drives more male feeding What We Don't Know Yet: Are there other hypotheses? Which one is correct? |
| Under this hypothesis, nest attentiveness and incubation feeding rates should be highest in species using nest sites that are exposed to extreme temperatures that can threaten embryo development or survival. | What it says: If the harsh climate theory is true, then birds nesting in very hot or cold places should have the highest rates of males bringing food and females staying on nests. What it does: Explains what evidence we'd expect to see if hypothesis 1 is correct Source/Type: Logical prediction based on the hypothesis Connection to Previous Sentences: This is NOT new information! This restates sentence 3 by spelling out its logical implications. Sentence 3 said harsh climates require more feeding - this just says "so we should see more feeding in harsh climates." Visualization: Prediction if hypothesis 1 is correct: Arctic terns (extreme cold): 95% nest time, 10 feedings/day Desert birds (extreme heat): 90% nest time, 8 feedings/day Temperate forest birds (mild): 70% nest time, 3 feedings/day Reading Strategy Insight: Feel relieved - this is simplification, not new complexity. The author is just making the prediction explicit. What We Know So Far: Hypothesis 1 predicts extreme climate = more feeding What We Don't Know Yet: Alternative explanations |
| An alternative hypothesis is that incubation feeding is constrained by nest predation; increased trips to the nest are hypothesized to attract the attention of predators. | What it says: Second possible answer: Maybe males don't bring food often because predators notice all the back-and-forth trips and find the nest. What it does: Introduces the second hypothesis (predation risk theory) Source/Type: Alternative scientific hypothesis Connection to Previous Sentences: This contrasts with sentences 3-4. Where hypothesis 1 focused on weather threats to eggs, hypothesis 2 focuses on predator threats from male activity. Visualization: High predation area: Male makes 8 trips/day → Hawks notice movement → Find and eat eggs Low predation area: Male makes 8 trips/day → No predators around → Eggs stay safe Reading Strategy Insight: Classic "alternative hypothesis" structure - we're not doubling complexity, just considering a different cause for the same variation. What We Know So Far: Two competing explanations - climate vs. predation What We Don't Know Yet: How the predation hypothesis would play out in practice |
| Females can consume more food in one foraging trip off the nest than a male can bring back to the nest in one trip, so the number of trips to the nest can be reduced by females obtaining most of their own food. | What it says: Female birds are more efficient food gatherers than males - one female trip gets more food than one male trip. So if females do most of their own food gathering, there are fewer total trips to the nest. What it does: Provides the biological mechanism that makes the predation hypothesis work Source/Type: Biological fact supporting the hypothesis Connection to Previous Sentences: This explains HOW the predation hypothesis would work. Sentence 5 said "more trips attract predators" - this explains how to reduce trips while still getting enough food. Visualization: Scenario 1: Female forages herself once → Gets 100 units of food Scenario 2: Male brings food 4 times → Gets 20 units per trip = 80 total food Result: Self-foraging = fewer trips + more food Reading Strategy Insight: This is just explaining the mechanics of hypothesis 2 - not introducing a third idea. What We Know So Far: Predation hypothesis works because females are efficient foragers What We Don't Know Yet: What this predicts we should observe |
| Therefore, under the nest predation hypothesis, species with a higher risk of nest predation should show increased foraging by females and lower rates of incubation feeding by males. | What it says: If the predation theory is correct, then in areas with lots of predators, we should see females leave the nest to get their own food more often and males bringing food less often. What it does: States the prediction that follows from hypothesis 2 Source/Type: Logical prediction from the predation hypothesis Connection to Previous Sentences: This mirrors sentence 4 exactly! Just like sentence 4 spelled out predictions for hypothesis 1, this spells out predictions for hypothesis 2. Visualization: Prediction if hypothesis 2 is correct: High predation areas: 70% nest time, 2 male feedings/day, female forages 3 times Low predation areas: 85% nest time, 6 male feedings/day, female forages 1 time Reading Strategy Insight: Perfect parallel structure! The passage is now complete and balanced - each hypothesis gets stated, then its prediction gets explained. This is the mirror image of sentence 4, so if you understood that, you understand this. Final Summary: • Climate hypothesis: Harsh weather → More male feeding • Predation hypothesis: More predators → Less male feeding • These predict OPPOSITE patterns! |
To present two competing scientific explanations for why bird species differ in how often males bring food to females sitting on nests.
In this passage, the author walks us through a scientific puzzle and offers two possible solutions:
There are two competing theories that make opposite predictions about male feeding behavior in birds: harsh climates should lead to more male feeding, while high predation risk should lead to less male feeding and more female self-foraging.
This question asks us to identify what the nest predation hypothesis implies about bird behavior when nest predation risk is high. We need to find the statement that logically follows from the predation hypothesis as described in the passage.
From our passage analysis, we know that the nest predation hypothesis makes a specific prediction: when predation risk is high, species should show "increased foraging by females and lower rates of incubation feeding by males." This happens because:
The passage analysis also revealed that the two hypotheses predict opposite patterns - while the climate hypothesis predicts more male feeding in harsh conditions, the predation hypothesis predicts less male feeding when predation risk is high.
Under the nest predation hypothesis, when predation risk is high, the primary concern shifts from keeping eggs warm to avoiding detection by predators. This means that the normal benefits of nest attentiveness (staying on the nest) must be weighed against the risk of attracting predators through frequent male feeding trips. The hypothesis suggests that in high-predation environments, it's actually safer to leave the nest unattended occasionally (so females can forage efficiently) rather than have males make multiple trips that could draw predator attention to the nest location.
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Key Evidence: "An alternative hypothesis is that incubation feeding is constrained by nest predation; increased trips to the nest are hypothesized to attract the attention of predators."
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