The equivalent of "this behavior too can be explained by the laws of natural selection" in physics would be "this object too follows the laws of Newtonian mechanics".
Usually solving the paradox (something looks redundant, but must be useful in some way) requires some creativity, but ultimately it's always a rather boring confirmation of the theory.
The danger of normal science is that scientists turn "it can be explained by the theory" into "it must be explained by the theory".
The energy required to maintain bodily structures mean that they tend to be relevant to evolutionary fitness. There are very few structures that are entirely irrelevant, even if the specific difference in form between different populations may be the result of genetic drift.
That said, I think your example would work by replacing it with "sexual selection." Don't know why bird feathers have complex micro-structures allowing them to reflect UV light? Let's just call it "sexual selection."
Obviously this ... seemingly useless feature must have been ... crucial to survival of this species.
I guess Thomas Kuhn calls this ordinary science. Explanation within the framework. But it's incredibly dull