What would a physics explanation of the mating behaviour of a bowerbird would look like, and who it would be useful to?

Biology is, in principle, reducible to physics but even if you were to solve any meaningful biological question in those terms - which is way beyond current abilities - the answer would get would have the wrong framing and explain at the wrong level. The meaningful answer for the bowerbird's wonderful mating ritual is one grounded in evolutionary theory not one grounded in particle physics.

What would a physics explanation of the mating behaviour of a bowerbird would look like, and who it would be useful to?

Biology is, in principle, reducible to fundamental physics but even if you were to solve any meaningful biological question in those terms - which is way beyond current abilities - the answer would get would have the wrong framing and explain at the wrong level. The meaningful answer for the bowerbird's wonderful mating ritual is one grounded in evolutionary theory not one grounded in particle physics.