After spending a few hours to generate the top, side and caged views for those, I noticed a little bug:
Some of the birds posess 4x4 pixel wings in the texture file, some 5x4 wings and some 6x4 wings. Whereas 4x4 and 5x4 are displayed correctly in the 3-D-model, the 6x4 texture is cropped.
This means, that the European Bee-eater (bird 0), the Carmine Bee-eater (bird 1), and the Lilac-Breasted Roller (bird 7) are missing the dark tips of their wings:
It's quite hard to see in the caged bird pictures, therefore I magnified and circled the missing bits.