Halcyon Creepers usually remain still, not making any sound or movement. When someone or something walks up to them, they turn around to look but otherwise remain like a statue. If a mob attacks them, they fly away. They are about as big as an Iron Golem. When in flight, their head turns a brighter gold, and the wings turn paler. When killed, they drop 1-3 Stable Gunpowder. They make absolutely no sound, even when hit. This trait is shared by Shadow Creepers.
Halcyon Creepers only spawn in Spring, but when it is Springtime, they are quite common. They come only in grasslands and forests.