The latter two terms, “bird” and “beast” (= wild animal), recall the unclean creatures listed in Leviticus 11. We may think of jackals, hyenas, vultures, and the like. The term “spirit” recalls the “demons” mentioned earlier in the verse (see also Mark 5:2; Luke 11:24). Together the “spirits” and “birds” and “beasts” represent all entities hostile to God’s purity. Whereas God is a God of life, these creatures(!) connect to death. And death, of course, is the bitter fruit of sin (Genesis 2:17; Romans 6:23).
2 And he called out with a mighty voice, “Fallen, fallen is Babylon the great! She has become a dwelling place for demons, a haunt for every unclean spirit, a haunt for every unclean bird, a haunt for every unclean and detestable beast.