Innate Spellcasting. The couatl's spellcasting ability is Charisma (spell save DC 13). It can innately cast the following spells, requiring only verbal components:

At will: detect evil and good

1/day each: create or destroy water, cure wounds, sanctuary

Shielded Mind. The couatl has advantage on saves against the scrying spell, as well as any spell or effect that would sense its emotions, read its thoughts, or detect its location.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: 6 (1d6 + 3) piercing damage, and the target must succeed on a DC 10 Constitution saving throw or be poisoned for 1 hour. 

Constrict. Melee Weapon Attack: +4 to hit, reach 10 ft., one Medium or smaller creature. Hit: 6 (1d6 + 2) bludgeoning damage, and the target is grappled (escape DC 13). Until this grapple ends, the target is restrained, and the couatl can't constrict another target.