Decomposed Wings. Skeletal aarakocra can't fly. 

Undead Nature. Skeletal aarakocra don't need air, food or water.

Talon. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. 
Hit: 4 (1d4 + 2) slashing damage.

Javelin. Melee or Ranged Weapon Attack: +4 to hit, reach 5 ft., or range 30/120 ft., one target. Hit: 5 (1d6 + 2) piercing damage.

Haunting. The aarakocra targets one creature it can see within 30 ft. of it. The target must succeed on a DC 14 Wisdom saving throw or is haunted by the ghost of the spirit of the aarakocra. Until the aarakocra chooses to end the haunting by selecting a new target or otherwise, the target is under the aarakocra's control and also takes 7 (1d10 + 2) necrotic damage. 
The target can do the Wisdom saving throw again whenever the aarakocra takes damage. The target is freed once the aarakocra ends the haunting or dies. Once the target is freed, it gets nightmares, hears ghostly spirits and /or has hallucinations of aarakocra skeletons for 15 (1d20 + 5) days.

Dark Magic. The aarakocra can use a bonus action to imbue its attacks for the next turn with dark magic, dealing an additional 3 (1d4 + 1) necrotic damage.

Howling Gyre. As a reaction, the aarakocra can let out a screech, dealing 2 (1d4) necrotic damage to every non-undead creature within 15 ft. that can hear it. Any living aarakocra that hears this screech turns into a skeletal aarakocra, and any creature that reaches 0 hp due to this screech turns into a skeleton as well.