Silly and extremely minor bug, feel free to put this at the absolute bottom of the priority list. :P
Tufted variants of the Risian Tropical Birds do not have their tuft tail feathers visible from below. I've tested this for all 6 variants (I admit to having no life and acquiring and keeping one of each bird, both Tufted and not) and all of them show this effect. The tufts are visible from above but not below, this only seems to affect the tail tufts and not the head tufts.
The universe has a wonderful sense of humor. The trick is learning how to take a joke.0