chirp, twitter, twittering
啁 centers on the light, repetitive sounds of small birds: chirping, twittering, and the act of making such sounds.
啁 combines 口 (mouth) with 周, which likely contributes the sound and may suggest a repetitive or surrounding quality, fitting the idea of continuous chirping.
A mouth 口 making the same sound over and over, like a bird's repetitive chirp: 啁 is twittering.
For トウ, imagine a tiny bird going 'tow-tow-tow' as it chirps: tow -> トウ, and the sound repeats from its mouth 口.