Passage Summary: A tree in the Indian Ocean is a descendant of a Hawaiian tree. Since the seeds die in salt water and the trees live high up in the mountains, they couldn't have floated there. The biologist concludes that birds must have carried the seeds across the ocean.

Conclusion: Seabirds are the most likely reason that a specific tree species moved from Hawaii to Réunion Island.

Reasoning: DNA shows the trees are related, but the seeds cannot survive in seawater and the trees grow in mountains rather than on the coast, ruling out ocean currents as a dispersal method.

Analysis: The biologist uses a process of elimination to reach the bird hypothesis, but the argument is currently a bit thin on positive evidence for birds. To strengthen the support, look for an answer that makes the bird theory more plausible. This could be evidence that certain birds actually travel between these two distant locations or that these birds are known to carry or eat these specific seeds without killing them. We want to move 'birds did it' from a mere possibility to a high probability.