Yǒu yì zhī niǎo diào jìn gāng.
False: 有一只鸟掉进缸。
Yǒu yì zhī niǎo diào jìn gāng lǐ.
True: 有一只鸟掉进缸里。
“缸”是个表示实体的名词,不能单独用来作“掉进”的宾语。须在“缸”后加上方位词“里”,表示处所。
As a noun denoting entity, 缸 can not be the object of 掉进 just by itself, but ought to be followed by the noun of locality 里, to show location.