Little bird

Birds or Little Bird are white birds with distinctive crests that are recurring ambient species in the Mario franchise ever since their debut appearance in Super Mario 3D Land. Occasionally, they even serve a gameplay purpose. Their appearance seems to be based off tits, a family of small passerine birds with similar body shapes and also notable for some species sporting crests.

Super Mario 3D Land
These birds make their first appearance in Super Mario 3D Land, serving as ambient creatures and usually appearing in flocks. When Mario or Luigi approaches them, they fly away.

Super Mario 3D World
In Super Mario 3D World, birds can also be found in various levels. In this game, they can occasionally appear in the title screen, where they fly away when the main cast of characters run through it.

Mario Kart 8 / Mario Kart 8 Deluxe
A flock of birds appear on the road in the following tracks in Mario Kart 8 and Mario Kart 8 Deluxe: Mario Circuit, Moo Moo Meadows, GBA Mario Circuit. SNES Donut Plains 3, N64 Royal Raceway,  3DS Piranha Plant Slide,  GCN Yoshi Circuit, and Dragon Driftway.

When racers approach them, they fly away, though after a set period of time without any racers, they return to the track. These birds are removed in the split-screen modes of the game.

Captain Toad: Treasure Tracker
Players can interact with the ambient birds in Captain Toad: Treasure Tracker. Normally, they fly away when Captain Toad or Toadette approaches them, but if they stand by a bird long enough, the bird flies and lands on their heads, which is detailed in Episode 11 of The Cat Mario Show.

Mario Sports Superstars
 Birds are one of the objects encountered in the grass in the stable mode of Mario Sports Superstars'' sport, Horse Racing. When players pass into them, they fly away and reveal a ? crate, which reveals a Mario Token. When players obtain 20 Mario Tokens, they unlock the Mario Token Crown, a special horse accessory for the head.