Question 105·Hard·Central Ideas and Details
In a 2021 study, researchers equipped 120 snow buntings with miniature geolocators to compare current migratory behavior with data collected in the 1980s. The devices showed that today’s buntings depart their northern Canadian breeding grounds an average of eight days earlier than they did four decades ago. The birds now spend about 20 percent more time at staging areas along the western shore of Hudson Bay. Yet they still reach their wintering sites in the central United States on nearly the same calendar dates as in the earlier data, a constancy the researchers credit to stronger prevailing tailwinds encountered during the latter half of migration.
Which statement about snow bunting migration is best supported by the information in the text?
For “best supported” questions, first list the passage’s concrete claims (especially numbers and comparisons). Then eliminate any option that (1) contradicts a stated fact (like arrival dates), (2) reverses a comparison (more vs. less), or (3) overgeneralizes a detail (e.g., changing “latter half” to “entire migration”). Choose the option that restates the passage’s relationships most directly without adding new claims.
Hints
Mark the three timing facts
Identify what the passage says about (1) departure timing, (2) time spent at staging areas, and (3) arrival timing.
Watch for words that overreach
Be cautious of choices that change the passage’s scope (for example, turning “during the latter half of migration” into “throughout the entire migration”).
Use contradiction to eliminate
If a choice says the birds arrive earlier or later, compare it to the line saying they reach wintering sites on nearly the same calendar dates.
Connect departure + staging time
Ask which choice best connects “leave earlier” with “spend more time at staging areas” in a way that fits the unchanged arrival dates—without inventing new facts.
Step-by-step Explanation
Restate what the question is asking
The question asks which statement about snow bunting migration is best supported by the passage. Choose the option that matches what is stated or what follows directly from the stated details, without adding new information.
Extract the key comparisons
Key facts in the text:
- Today’s buntings depart their breeding grounds 8 days earlier than in the 1980s.
- They now spend about 20 percent more time at staging areas along the western shore of Hudson Bay.
- They still reach their wintering sites in the central United States on nearly the same calendar dates as before.
- Researchers credit this timing constancy to stronger prevailing tailwinds encountered during the latter half of migration.
Eliminate choices that contradict or overstate details
Check each choice against the passage:
- Choice A overstates the tailwind claim by saying tailwinds occur throughout the entire migration, but the text specifies the latter half.
- Choice B contradicts the passage: it says buntings spend less time at staging areas, but the text says about 20% more time.
- Choice C contradicts the passage: it predicts a later arrival, but the text says arrival is on nearly the same calendar dates.
- Choice D matches the stated pattern of earlier departure plus more time at staging areas, which supports the idea of longer stopovers helping balance the schedule.
Select the best-supported statement
Therefore, the statement best supported by the passage is: Snow buntings offset their earlier departure by extending the duration of stopovers along their migration route.