Male bowerbirds construct elaborately decorated nests, or

This question is testing CORRELATION v. CAUSATION logic.

Given:
The building styles of bowerbirds of the same species are different in different locations.

Conclusion:
Building styles are culturally acquired, not genetic.

Logical Gap:
- are these birds in different locations genetically similar? Couldn't they have differences in genetic traits specific to certain locations that might account for these differences?

To strengthen:
We need further information to suggest that building information is not inherited but rather learned.

A. There are more common characteristics than there are differences among the bowerbuilding styles of the local bowerbird population that has been studied most extensively.
This doesn't strengthen. We're given that there ARE differences, and we want to strengthen the explanation for why. Knowing that there are also similarities is not helpful.

B. Young male bowerbirds are inept at bowerbuilding and apparently spend years watching their elders before becoming accomplished in the local bower style.
If young ones are inept, that suggests that they don't have the knowledge innately, and that they must learn it. Correct!

C. The bowers of one species of bowerbird lack the towers and ornamentation characteristic of the bowers of most other species of bowerbird.
This merely explains what one of the differences is. We don't care about the particulars of the differences; we just care WHY there are differences.

D. Bowerbirds are found only in New Guinea and Australia, where local populations of the birds apparently seldom have contact with one another.
If different populations don't interact with each other, they might have more distinct genetic traits as well as distinct cultural knowledge. This does not help to explain that differences are caused by nurture and NOT by nature.

E. It is well known that the song dialects of some songbirds are learned rather than transmitted genetically.
This argument is not concerned with songs. It's possible for some traits to be learned and others to be genetic, so this is irrelevant to building styles.

The answer is B.