岛 (dǎo) 'island' is an associative phono-semantic compound. It combines 鸟 (niǎo, bird) with 山 (shān, mountain): a mountain in the sea where birds settle and rest. The bird element also hints at the sound. The character names a piece of land surrounded by water. The traditional form is 島.

Origin

associative / phono-semantic compound

Root

鸟 (niǎo, bird) + 山 (shān, mountain)