Avian Chimera Experiment

Keen Sight and Smell.  The experiment has advantage on Wisdom (Perception) checks that rely on sight or smell.

Flyby.  The experiment doesn’t provoke an opportunity attack when it flies out of an enemy’s reach.

Hollow Bones.  The experiment’s hollow bones causes it to be vulnerable to bludgeoning damage, but also grants it proficiency in Dexterity saving throws.

Multiattack.  The experiment makes three attacks: one with its claws, one with the peryton's antlers, and one with either the owlbeak's beak or the cockatrice's bite.  If available, it will always use the cockatrice's bite.

Claws.  Melee Weapon Attack: +6 to hit, reach 5 ft., one target.  Hit: 10 (2d6 + 3) slashing damage.

Antlers.  Melee Weapon Attack: +6 to hit, reach 5 ft., one target.  Hit: 8 (2d4 + 3) piercing damage.

Beak.  Melee Weapon Attack: +6 to hit, reach 5 ft., one target.  Hit: 8 (2d4 + 3) piercing damage.

Bite (Recharge 6).  The cockatrice head makes a bite attack against a single creature.  Melee Weapon Attack: +3 to hit, reach 5 ft., one target.  Hit: 5 (2d4) piercing damage and the creature must make a DC 14 Constitution saving throw against being magically petrified.  On a failed save, the creature begins to turn to stone and is restrained.  It must repeat the saving throw at the end of its next three turns. One success ends the effect. After three failures, the creature is petrified for 1 hour.