In the vertebrate retina, amacrine and ganglion cells represent the most diverse 
cell classes. They can be classified into different cell types by several 
features, such as morphology, light responses, and gene expression profile. 
Although birds possess high visual acuity (similar to primates that we used here 
for comparison) and tetrachromatic color vision, data on the expression of 
transcription factors in retinal ganglion cells of birds are largely missing. In 
this study, we tested various transcription factors, known to label 
subpopulations of cells in mammalian retinae, in two avian species: the common 
buzzard (Buteo buteo), a raptor with exceptional acuity, and the domestic pigeon 
(Columba livia domestica), a good navigator and widely used model for visual 
cognition. Staining for the transcription factors Foxp2, Satb1 and Satb2 labeled 
most ganglion cells in the avian ganglion cell layer. CtBP2 was established as 
marker for displaced amacrine cells, which allowed us to reliably distinguish 
ganglion cells from displaced amacrine cells and assess their densities in 
buzzard and pigeon. When we additionally compared the temporal and central fovea 
of the buzzard with the fovea of primates, we found that the cellular 
organization in the pits was different in primates and raptors. In summary, we 
demonstrate that the expression of transcription factors is a defining feature 
of cell types not only in the retina of mammals but also in the retina of birds. 
The markers, which we have established, may provide useful tools for more 
detailed studies on the retinal circuitry of these highly visual animals.