No, this is an old error that was never fixed. The baby has a description problem because babies don't use the standard data. It can be fixed with any plain text editor.
After line 354( or anywhere inside of "dict"), of ".../mods/AricsExpansion/scripts/characters/description.gd", a new line needs to be added for feathers_and_fur. I just copied the normal entry from lower down in the file:
feathers_and_fur = '$His body is sparsely covered with [color=aqua][feathercolor] bird-like feathers[/color]. Beneath that is thick, soft [color=aqua]fur of [furcolor]',
Although [furcolor] doesn't work because it was only added to the normal description function, it doesn't cause any errors.
Edit: another description line is missing from "dict" and can also be added next to the feathers_and_fur line.
fullfeathers = '$His body is covered with [color=aqua][feathercolor] feathers[/color]. ',
Since this change is made to the mod file, you will need to re-apply the mods to update the game files. No need to go through the full install process, simply press Apply and restart when done.