type of deciduous tree, grey starling
椋 refers to a type of deciduous tree, and by extension the grey starling, likely because the bird is associated with that tree.
椋 combines 木 (tree) with 京, which likely contributes the sound. The character was created to name a specific tree species.
A tree 木 beside a capital 京: imagine a tall deciduous tree growing in the capital, where grey starlings gather.
For リョウ, picture a grey starling perched on the tree singing a clear 'ryo' note: ryo -> リョウ.