When Leach\'s storm pretrels fly back to their burrows on islands in the ocean a

Question

When Leach's storm pretrels fly back to their burrows on islands in the ocean at night, they:
a) drop to the forest floor downwind of their burrows and then walk upwind to the burrow entrance
b) tend to land closer to their burrows in still air than when it is windy
c) follow less direct routes to burrows in still air than in wind
d) fail to avoid obstacles in the path to their burrows


What do these observations suggest about the sensory basis of burrow location by these birds and why do you conclude this from observations A to D?

Explanation / Answer

1. ANS: According to the given question the four options are correct.

Explanation: Petrels returning to their burrows at night hovered above the thick spruce-fir canopy in the vicinity of the burrow before plummeting to the forest floor a few metres downwind of their burrows. They then walked upwind to their burrows. Birds landed closer to, and followed more circuitous routes to, their burrows in still air than in a wind. They failed to avoid obstacles in the path to burrows, often failed to locate accurately burrow entrances on first trial, and vocalized only after entering the burrow.
2. ANS: In a Y-maze olfactorium, captive breeding petrels chose an air current coming from their own nest material in preference to one from similar materials collected on the forest floor. Petrels taken from burrows and released that same night did not return within a week if their external nares were plugged or if their olfactory nerves were transacted. They did return if not operated on or if only subjected to sham operations. These results support an olfactory guidance system in burrow location and argue against visual or auditory guidance.

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