Thrummingbird is a uncommon Creature — Phyrexian Bird Horror card from Scars of Mirrodin (SOM), collector number 47. Current market price: $0.37 (foil $4.45), TCGplayer market prices via Scryfall.
Flying Whenever this creature deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)