thrush, (kokuji)
鶫 is a Japanese kokuji that specifically names the thrush bird. It has no broader abstract meaning beyond this single animal reference.
鶫 is a kokuji (Japanese-made kanji) combining 柬 (possibly for sound or as a simplified element) with 鳥 (bird) to represent the thrush. The exact historical motivation for the left component is uncertain.
The right side 鳥 clearly signals a bird. The left side 柬 looks like a bundle of twigs, perhaps the thrush's nest. Together they point to the thrush.
For トウ, imagine a thrush singing a clear 'toe' note: toe -> トウ, and the bird on the right chirps it.