Remarkably differently engineered beaks!
The scaly breasted mulia have massive structures I guess for crushing things whereas the song bird has a long delicate beak for small insects and nectar, perhaps!
Yet, I’m on a genome level there might be simply duplication of sections of DNA or some minor modifications teasing out these differences. This to me is so fascinating.
As long as there is a varied niche to feed in, birds will adapt their anatomy and behavior to thrive there.
Imagine, this amazing propensity is already present once organic chemicals form in ocean hot springs!
That to me is mind boggling!
Asher