Unwanted listener. If the undergrowth scavager is hidden somewhere and listening to someone talking he understands each language but cant speak it yet, but can quote what he heard. 

Quick and quiet. The undergrowth scavager gets +10 ft. movement speed when stealthing. And is seen as a small creature when looked at from the side. 

Multiattack. The undergrowth scavager makes two claw attacks. 

Adrenaline multiattack. The undergrowth scavager makes three claw attacks. This is only useable when below 27 hit points.

Claw. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 10 (4d4 + 2) slashing damage. If the target is a creature, it must succeed on a DC 12 Wisdom saving throw or be frightened until the end of the undergrowth scavagers next turn.

Terrifying Glare. The undergrowth scavager targets one creature it can see within 30 feet of it. If the target can see the undergrowth scavager, the target must succeed on a DC 15 Wisdom saving throw or be magically frightened until the end of the scarecrow’s next turn. The frightened target is paralyzed. The creature gets disadvantage when the undergrowth scavager is in dim light or darker.

Hide. The undergrowth scavager can use hide as a bonus action and is hidden, creatures must suceed a DC 15 check to spot the undergrowth scavager. If this is performed in a forest or a swamp other creatures must suceed a DC 18 Perception check to spot the undergrowth scavager but its true form is only revealed by a DC 20 Perception check.