Usually a tiny bird automaton in a decorated metal, tortoise shell or composition case. The bird pops up from under a spring-loaded lid, moves its wings and, on the higher quality, early models, the head. A bird song is produced from a bellows-operated flute or whistle within the box.
Also includes birds enclosed in a cage and/or fixed on a perch that may or may not move but make whistling/birdlike sounds and do not pop out of a box.