Rare term for the lesser cuckoo (Cuculus poliocephalus). In modern Japanese, this bird is almost always called 時鳥 (ほととぎす) or ホトトギス. 橘鳥 is a literary or poetic name, and the reading たちばなどり is seldom used in everyday speech.
See also: ホトトギス
The name 橘鳥 (たちばなどり) sometimes appears in old waka poems as an alternate name for the lesser cuckoo.
The kanji 橘 (tachibana, a type of citrus) and 鳥 (bird) combine to form a poetic name for the lesser cuckoo. The exact origin of this name is uncertain, but it likely derives from classical Japanese poetry or seasonal associations.