Mockingbird is a rare Creature — Bird Bard card from Bloomburrow (BLB), collector number 305. Current market price: $6.21 (foil $24.55), TCGplayer market prices via Scryfall.
Flying You may have this creature enter as a copy of any creature on the battlefield with mana value less than or equal to the amount of mana spent to cast this creature, except it's a Bird in addition to its other types and it has flying.