Chapter X 

 CLASSIFICATION OF THE OCULAR FUNDI OF BIRDS 



The particolored avian background, as seen 

 by the ophthalmoscope, although of great 

 variety, may be divided into two major 

 categories and each of these into five sub- 

 divisions, as follows: 



A. The avascular fundus, in which there 

 are no visible retinal or choroidal blood- 

 vessels. 



This class resolves itself into (a) those 

 avascular eyegrounds in which the predomi- 

 nant color is light gray or gray-blue. These 

 fundi are comparatively rare, but examples 

 of them are found in the Varied Bunting 

 (Plate LIV) and the Ipecaha Rail (Plate 

 XIII). 



(b) Dark gray, deep gray-blue or slate- 

 colored avascular fundi are quite common. 

 The Harlequin Quail (Plate VIII), English 

 Sparrow (Plate LIII), Derby Tyrant (Plate 

 XLIX), Brush Turkey (Plate VII), Yarrell's 

 Curassow (Plate VI), Sulphur-crested Cocka- 

 too (Plate XLI), and the European Bittern 

 (Plate XXI) are samples. The fundi of the 

 Crested Coot (Plate XII) and of the Black 

 Hornbill (Plate XLIII) belong to this sub- 

 division but they also show a greenish tinge. 



(c) Yellow, orange and orange-red bloodless 

 fundi belong almost exclusively to Night 

 Birds, or to those that use their eyes for 

 both diurnal and nocturnal visualization. 

 Such fundi are seen in the Apteryx (Plate 

 IV), Gannet (Plate XXIX), and the Black- 

 footed Penguin (Plate XIV). The corres- 

 ponding class of vascular fundi is a much 

 larger one. 



(d) Fundi of a brownish or russet color, 

 showing no vascular supply, are rather com- 

 mon. Examples are seen in the Amazon 

 Golden Parrot (Plate XXXIX), South Amer- 



ican Ostrich (Plate II) and the Cassowary 

 (Plate III). 



(e) Bicolored or multicolored fundi devoid 

 of visible blood-vessels are but infrequently 

 encountered. The fundus of the Nubian 

 Ostrich (Plate I) is mostly of a light chocolate 

 shading to red; also the Bluebird (Plate LI) 

 exhibits a background mostly light gray-blue 

 but has also a small red-brown area or zone 

 dotted with black. 



B. The vascular fundus oculi is one in 

 which the choroidal capillaries show more or 

 less distinctly. In some instances the blood- 

 vessels are barely visible; in others they 

 cover the whole background and are the most 

 conspicuous objects in it. The vascular fun- 

 dus is subdivided like the avascular back- 

 ground. 



(a) Light gray or gray -blue fundi, more 

 common than A (a), are found in the Wheat-ear 

 (Plate LII), the Cormorant (Plate XXVIII), 

 and the Glossy Ibis (Plate XXIII). 



(6) Dark gray, deep gray-blue or slate- 

 colored vascular fundi constitute the com- 

 monest examples of colored fundi so far seen 

 by the writer. They are found, among 

 others, in the European Cuckoo (Plate XLV), 

 the Wonga Wonga Dove (Plate IX), the 

 Puffin (Plate XV), Sulphur-breasted Toucan 

 (Plate XL VI), Spoonbill (Plate XXV), Great 

 Spotted Woodpecker (Plate XLVIII), Blue- 

 crowned Jay, with a greenish tinge (Plate 

 LVI), Common British Blackbird (Plate 

 LVII), the Night Heron (Plate XX), Ameri- 

 can Jabiru (Plate XXIV), Law Bird of Paradise 

 (Plate LV), Lammergeier (Plate XXXII). 



(c) Yellow, orange or vermilion fundi show- 

 ing choroidal blood-vessels are, as in the A(c) 

 class, found almost entirely in birds with 



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