Hawk

A hawk is a scout, a familiar, a ranger's companion, and a messenger. It has no attack worth rolling and 1 HP, so the moment it enters combat against anything competent, it dies. Run the hawk as a sensor with wings: 60 ft. fly, Perception +6, passive 16, and the ability to be in the air looking down while the party walks the road below.

Out of combat, the hawk is one of the most useful low-CR allies in the bestiary. It scouts ahead, returns to a glove, lands on a shoulder, and the ranger can describe what it saw. A wizard with Find Familiar can take the hawk form for the same reasons. Use it to telegraph encounters without forcing a Perception check from the players: the hawk circles, stoops, screams, and the party knows there's something on the ridge before initiative ever rolls. That's a free rhythm tool you should not waste.

In combat, the hawk's job is to leave. 1 HP at AC 13 means any AoE, any incidental damage, any halfway-decent shot from an enemy archer, and the hawk is dead. The party has 60 ft. of fly speed to play with, so use it: the hawk lifts the squirrel-sized item the wizard needs out of the goblin's pouch, or carries a note to the next room, or perches on the chandelier to keep watch while the party negotiates. Don't roll it into the fight. Beasts at Int 2 don't make heroic stands, and the player whose familiar dies for nothing will be sour for the rest of the session.

Give the hawk a name and a single quirk before the session. Players who only have one line of personality for an animal companion always come back to that one line, which is exactly what you want.

A hostile hawk on its own is barely an encounter. The framing that works is a flock or a trained raptor: a falconer's bird trained on a target, a witch's familiar dive-bombing the party from cover, or a dozen wild hawks defending a mountain nest. Solo, the hawk plinks for nothing and dies in one hit. The threat has to be the swarm or the handler.

Run the trained raptor as a delivery mechanism. The hawk swoops in, drops something on the party (a vial of acid, a thieves' tool, a marked feather that lets the handler scry on them), and is gone before initiative can really matter. Don't let the party shoot it down in round one, since 60 ft. of fly speed and 10 ft. of starting altitude usually puts it out of range after the drop. The party loses one round to confusion, then the real encounter starts.

Run the wild flock as atmospheric pressure rather than damage. Six hawks, 1 HP each, screaming and stooping at faces. Anyone trying to climb the cliff to the nest takes a hawk-attack interrupt that costs concentration on whatever spell they were holding, and a failed Dex save means they slip 10 feet down. The fight is the climb, not the birds.

Show the falconer's whistle, then the dive. The party should always be able to trace the hawk back to a person, because the person is the actual encounter.