68 BUZZARD— C^CA 



breed, yearly in the New Forest, does not come into the sub- 

 family Buteoninx, but is probably the tj^pe of a distinct group, 

 Perninse,^ of which there are other examples in Africa and 

 Asia. The so-called " Turkey-Buzzard " is one of the American 

 Vultures. 



c 



Cu^CA, a pair of blindsacs or lateral dilatations of the gut, 

 mai'king the beginning of the rectum. "When the caeca are large the 

 rectum is shut off from the ileum or small intestine by a valvular 

 sphincter, which allows the faecal matter to ascend from the rectum 

 into the caeca, but prevents it from passing back into the ileum. 

 The caeca vary extremely in size in the different groups of Birds ; 

 they attain their greatest size in those that are herbivorous, are 

 small or hardly functional in most that live on animal food, and are 

 altogether absent in fruit- and grain-eaters. There are, however, so 

 many exceptions to this broad generalisation, that an enumeration 

 is advisable, especially since a certain taxonomic value cannot be 

 denied to these organs. 



It is highly probable that originally all Birds possessed caeca, 

 and that, according to the diet, these were either further developed 

 or reduced in size or even lost ultimately. Hence the mere 

 presence of cseca in a bird is of less taxonomic value than their 

 state of development ; they are either functional, or without func- 

 tion ; their absence is only the last step of their degeneration. 



1. The caeca are large and of great functional importance in 

 Struthio, Ehea, Apteryx, Ciypturi, Gallina?, Pteroclida?, Grallae, and 

 Anseres, i.e. in birds which are chiefly herbivorous ; also in many 

 worm-eating Limicolas, for instance in the Avoset, Lap"\\dng, Ringed 

 Plover, GEdicnemus, Thinocorys, Attagis, and the Corncrake ; lastly in 

 the Owls, Nightjars, Boilers, Bee-eaters, and Cuckoos, i.e. birds which, 

 ■with the exception of the first group, are strictly insectivorous. 



2. The caeca are distinctly functional, but comjDaratively short, 

 in Casuarius, Dromaeus, Grus, Turnix, many Anatidi^e (vegetable- 

 eaters with a great predilection for animal food), Limicoke and 

 Eallidae, like the Golden Plover, Numenius, Totanus, Gallinago, 

 Chionis, Porphyrio, Porzana ; the piscivorous Spheniscidte, Peli- 

 canus, Podicipes, Uria, Colymbus ; Merops, and Phoenicopterus. 



3. The caeca are quite degenerated and functionless, being 

 either {a) reduced to small wartlike or vermiform appendages, as 

 in some Spheniscida?, Herodii, Pelargi, Steganopodes, Larida?, Strep- 



^ The name Pernis was given in 1817 by Cuvier {Rtgne Anim. i. p. 322), who 

 said it was used by Aristotle ; but the latter has only -wTipvis [Hist. Anim. ix. 36),, 



i 



