yellow-white mottled songbird
鷏 refers to a specific kind of bird: a yellow-white mottled songbird. Its meaning is narrow and ornithological, without broader abstract extensions.
鷏 combines 真 (likely a phonetic component) with 鳥 (bird), forming a phono-semantic character for a specific bird name. The exact historical development is uncertain.
The left side 真 (truth) and the right side 鳥 (bird) combine to suggest a bird whose true colors are a yellow-white mottled pattern. Picture a songbird with a mottled coat that reveals its true identity.
For テン, imagine ten (テン) little yellow-white mottled songbirds perched on a branch, all singing together. The number ten cues テン while the birds match the meaning.