Source: Waterdeep - Dragon Heist

Wondrous item, uncommon

After you write a message of fifty words or fewer on this magic sheet of parchment and speak a creature's name, the parchment magically folds into a Tiny paper bird and flies to the recipient whose name you uttered. The recipient must be on the same plane of existence as you, otherwise the bird turns into ash as it takes flight.

The bird is an object that has 1 hit point, an Armor Class of 13, a flying speed of 60 feet, a Dexterity of 16 (+3), and a score of 1 (-5) in all other abilities, and it is immune to poison and psychic damage.

It travels to within 5 feet of its intended recipient by the most direct route, whereupon it turns into a nonmagical and inanimate sheet of parchment that can be unfolded only by the intended recipient. If the bird's hit points or speed is reduced to 0 or if it is otherwise immobilized, it turns into ash.

Paper Birds usually come in small, flat boxes containing 1d6 + 3 sheets of the parchment.