@Sugar Morning
I wanna say we had one of those cat creatures from the movie in one of the prior collabs. I can’t find it (probably not tagged well), but I’m pretty sure we had one that was allowed because it was a shorter character and scaled well.
Scaling is one of the major issues with anthromorphic characters - they stand a lot taller than feral characters. When one character is standing 2-3 times taller than the pony next to it, that makes it really tricky to layer everything together without one character standing out too much or taking out too much space.
If you can draw one of those bird characters in a way that it’s not too tall compared to a pony, and not taking up too much screen space without looking odd, I’d accept that. And I’m confident that you’d be able to pull that off, so I’ll say yes. You can do that.
(note: I’m saying yes to Sugar Morning specifically, this is not a blanket approval to anyone. Anyone else would still have to ask and it’d be subject to art style, character design, etc)