栖 appears in 栖息 (to perch, inhabit), 栖息地 (habitat), and 两栖 (amphibious), which literally means 'dwelling in two environments'. An old reading xī survives only in the archaic, reduplicated 栖栖 (restless), which is not used in modern Chinese.
Left 木 is the tree radical, indexing 栖 in the wood and arboreal family. It carries the meaning directly: a bird perching is a creature settling onto a tree branch. Same family: 林, 森, 枝.
Right 西 supplies the sound, shifting from xī to qī. It originally pictured a bird settling into a nest at sunset, exactly the action 栖 describes, so the phonetic doubles as a semantic hint: tree plus nest-shape gives a perching bird.
