yellow-white mottled songbird
鷆 refers to a specific kind of bird: a yellow-white mottled songbird. The meaning is narrow and ornithological, without broader abstract extensions.
鷆 combines 鳥 (bird) with 眞, which likely contributes the sound. The character was created to name a specific bird species.
The bird radical 鳥 on the right tells you it's a bird. The left side 眞 looks like a detailed eye under a lid, perhaps the bird's distinctive mottled eye pattern.
For テン, imagine ten of these mottled songbirds perched in a row: ten -> テン, and their yellow-white feathers catch the light.