I found the sources for scavenger's sound effects and more

I wanted to know where do the scavenger sound effects come from, since a lot of different pieces of media also used it. A couple people on the internet said this sound is also used in Moana, so I tried seeing if somebody made a list of sound libraries used in that movie and sure enough, the Soundeffects Wiki lists it as Sound Ideas, CARTOON, CHICKEN - LOUD SINGLE SQUAWK. I downloaded the library from The Internet Archive and I found the original file, which had the scream and idle sounds, but the attack sounds were missing, so I kept digging and found the sound used in scavenger's eating sound, EATING, CARTOON - BIG GLOPPY CHEWING, FOOD and the sound of opening a gate, LARGE DRAWBRIDGE LOWERING TO GROUND, LONG, DOOR, CASTLE and crawler's hissing sound, SMALL STREAM OF WATER SQUIRTING, CARTOON. I found this post mentioning the Sound Ideas Lucasfilm SFX Library and Sound Ideas Series 4000 libraries, so I downloaded them and found some more sounds.

Human male hurt sounds:
MALE, AGONY, HUMAN, HORROR 2
MALE, AGONY, HUMAN, HORROR 3

Zombie death sound (slowed down) - MALE, LONG, HUMAN, HORROR 5

Some or warg's sounds - BADGER - GROWL & HISS, ANIMAL

Shadow beast's death sound - CAT, TIGER - GROWLS, C.U. GROWLS, SNARLS, ROARS, ANIMAL

The rest of scavenger's sounds:

DOLPHIN - DISTANT CALLS, ANIMAL
SEAL LION - BARKS, SCREAMS, SNARLS, GRUNTS, ANIMAL

And the night and swamp ambient sounds:

AMBIENCE, FOREST - FOREST, SPOOKY NIGHT
AMBIENCE, COUNTRY - RURAL, TREEFROGS

Someone could probably make a mod that replaces these assets with higher quality sounds