If you have any ideas yourself, please feel free to share them here!
I recently came across a very small family of birds named Anhimidae, or more commonly known as "Screamers." There's only 3 species in the family, but they're all beautiful birds and make some of the most fascinating sounds. One in particular, the Horned Screamer, I think has some phenomenal potential for sound design and environmental immersion in more tropical areas. Here's a short Youtube video of two Horned Screamers and a small portion of the family's sound range.
I think this bird could be used as the basis for some pretty interesting creatures!