Avian Changeling

Changeling is a characteristic-defining ability. “Changeling” means “This object is every creature type.” This ability works everywhere, even outside the game. See rule 604.3.

Flying is an evasion ability.

A creature with flying can’t be blocked except by creatures with flying and/or reach. A creature with flying can block a creature with or without flying. (See rule 509, “Declare Blockers Step,” and rule 702.17, “Reach.”)

Multiple instances of flying on the same creature are redundant.