For bird species in which females are the sole incubators, a male can

     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.

1. 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?

A. It is less threatening to embryo development to leave a nest unattended at times than it is to draw attention to the nesting site.
B. Embryos will be most successful in situations where females forage for less than half of their own food during incubation.
C. Incubation feeding is likely to increase steadily as embryos develop.
D. Attempts at incubation feeding by males will be rejected by incubating females.
E. Incubation feeding will occur only when a harsh microclimate is combined with a high risk of predation.


2. According to the nest predation hypothesis as it is described in the passage, which of the following should occur when a bird species in which females are the sole incubators is at high risk of nest predation?

A. Females will go without food in the interest of keeping the nest inconspicuous.
B. Females will leave the nest unattended periodically in order to forage for food for themselves.
C. Males will supply all of the females’ food throughout the incubation period.
D. Males will bring food to females only at times when embryo development is threatened by extreme temperatures.
E. Males will obtain most of the females’ food, but females will occasionally forage for food themselves.


3. Which of the following best describes the structure of the passage as a whole?

A. A scientific debate is noted, and then certain research methods that could help resolve that debate are discussed.
B. A scientific study is described, and then various implications of that study are summarized.
C. A scientific question is introduced, and then potential answers to that question are discussed.
D. A hypothesis is presented, discussed, and then rejected in favor of a second hypothesis.
E. Factual information about a certain situation is provided, and then contradictory interpretations of that information are noted.