Figure 1.
Photos of the brains of three species of parrots.
A, the Kakapo (Strigops habroptilus); B, Kea (Nestor notabilis); and C, Sulphur-crested Cockatoo (Cacatua galerita). The dotted lines outline the left optic lobe of all three species. Abbreviations refer to the following: OB, olfactory bulbs; W, Wulst; Cb, cerebellum; and TeO, optic lobe. Scale bar = 10 mm.
Figure 2.
Scatterplots of each of the four visual brain regions measured against total brain volume.
A, optic tectum (TeO); B, nucleus rotundus (nRt); C, entopallium; and D, Wulst. All measurements in mm3. The solid lines indicate the least-squares linear regression lines and dotted lines indicate the phylogeny-corrected 95% confidence interval. The diamond represents the Kakapo (Strigops habroptilus), the filled circle represents the Kea (Nestor notabilis) and open circles represent other parrot species included in the analyses.
Figure 3.
Scatterplots for each of the parameters measured from the eye.
A, optic foramen diameter, B,C,D, eye size, and E, eye shape. Kakapo (diamond), Kea (filled circle), Kaka (triangle) and all other parrots (open circles). The solid lines indicate the least-squares linear regression lines and dotted lines indicate the phylogeny-corrected 95% confidence interval. F, is a boxplot of orbit orientation (in degrees) measured in the Kakapo and 64 other parrot species. The box plot shows the smallest observation (sample minimum), lower quartile (Q1), median (Q2), upper quartile (Q3), and largest observation (sample maximum). Outliers are shown as open circles and also a diamond for the kakapo.
Figure 4.
Photomicrographs of transverse sections through the retina of five species of birds.
A, Kakapo (Strigops habroptilus), B, Barn Owl (Tyto alba), C, Sulphur-crested Cockatoo (Cacatua galerita), D, Eastern Rosella (Platycercus eximius), and E, Chicken (Gallus gallus domesticus). Aa and Ab are photomicrographs of peripheral and central photoreceptors respectively in the kakapo retina at 100 times magnification. Ba is a higher magnification image of the photoreceptors in the Barn Owl. The arrows indicate cone photoreceptor cells. Retinal tissue was stained with cresyl violet. Abbreviations are as follows: RPE, retinal pigmented epithelium; OS/IS, outer segment/inner segment; ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer. Scale bar = 25 µm.
Table 1.
Shows average thickness for central and peripheral retina and retinal layers in diurnal and nocturnal species.