CHAPTER XXIV 



THE CUCKOO-LIKE BIRDS 



(Order Cuculiformes) 



|HIS order is the last great group in which the ambiens muscle, already 

 spoken of as being of high classificatory value, is present, in addition 

 to which all possess a "yoke-toed" (zygodactylous) foot, and the 

 bridged or desmognathous type of palate. This so-called "yoke-toed " 

 condition is brought about by the first and fourth toes being permanently di- 

 rected backward, a manner quite different, it will be recalled, from the way in 

 which it is accomplished in the Trogons, though similar to the arrangement in 

 Woodpeckers, Puff-birds, Barbets, etc., and on which account they were all for- 

 merly placed together. However, the arrangement of the deep tendons of the 

 foot is sufficient in conjunction with the above-mentioned characters to dis- 

 tinguish the Cuculiformes, and is very different from that in the Woodpeckers 

 and allied forms. In these tendons the anterior portion splits into three branches, 

 which supply respectively the second, third, and fourth toes, while the posterior 

 portion supplies only the hind toe, the two tendons being bound together by a 

 band (vinculuni). This type of tendon arrangement is of quite common occur- 

 rence, being that which obtains in Gallinaceous birds, Herons, Cranes, Rails, 

 Gulls, Auks, etc., and differs from that in the passerine birds simply in having 

 the tendons bound together by a vinculum or band. 



The Cuculiformes embraces two suborders, the Cuculi, or Cuckoos, and Plan- 

 tain-eaters, and the Psittaci, or the extensive group of Parrots. In the first sub- 

 order the young are born naked and do not pass through a downy stage before 

 acquiring their feather covering, while in the typical members the contour feath- 

 ers are without an aftershaft, and the oil-gland is present but nude. The tail- 

 feathers are normally ten in number, but in some New World forms there are 

 but eight. f In the Parrots (Psittaci), on the other hand, the young pass through a 

 downy stage, the contour feathers possess an aftershaft, and the oil-gland is usu- 

 ally present and tufted, though entirely wanting in a few genera. As regards 

 the tail-feathers, the normal number is twelve, a single Papuan genus possessing 

 fourteen. Of the structural characters it may be mentioned that the Parrots 

 possess the permanently zygodactylous feet, a movable upper mandible, and a 

 short, stout, strongly hooked bill, while there are no caeca and the gall- 

 bladder is usually absent. 



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