that connect the Orders and Families of Birds. 455 



are strictly and constantly disposed in pairs : and they are con- 

 sequently the only groups which constantly benefit by that con- 

 struction in climbing. The external hind toe of the other Scan- 

 sores is retractile : and these birds are never observed to climb, at 

 least to that extent which is common to the two families in ques- 

 tion. We may thus venture, I think, to separate the Parrots and 

 Woodpeckers from the other families, and to associate them toge- 

 ther, in consequence of their affinity in these essential characteris- 

 tics of the tribe. In this point of view they will compose its normal 

 groups, as climbers par eicelleiice, differing, however, as to the 

 mode in which they climb ; the Parrots using the foot chiefly in 

 grasping the object which assists them in their ascent, and in 

 conjunction with the bill ; while the Picidce rely upon the strength 

 and straightness of the hind toes in supporting them in a per- 

 pendicular position on the sides of trees ; in which posture they 

 are also assisted by the strong shafts of the tail-feathers. While I 

 was influenced by these general points of coincidence, in placing 

 the Psittacida and Picidce together*, I recognised a group which 

 appeared to intervene between them, and to diminish the appa- 

 rent distance that exists even in the form of their bill. That im- 

 portant group, which comprises the Linnean Barbets, evidently 

 exhibited the expected gradation in the structure of that mem- 

 ber ; the bill of Pogonias, 111. approaching most nearly that of 

 the Parrots, by its short, strong, and hooked conformation t, 



* There are some minuter and less essential points also in which this approxima- 

 tion is evident. Some of the Fsittacida, among which I shall particularize the Psit- 

 tacus Alexandri, Linn., and its congeners, partially employ the tail in supporting 

 themselves as they climb, in a corresponding manner with the Woodpeckers. I make 

 this remark from my own observation. The tongue also peculiar to the family may be 

 observed to become slenderer, and, as is said, more extensible, in that group of which 

 P. aterrimus, Gmel. is the representative ; thus evincing an approximation, slight in- 

 deed, but still an approximation, to the bill of the Woodpeckers. 



f It also comes nearer to them by its frugivorous habits. " lis (Sc. les Barbicans) 

 inangent plus de fruits que les autres esp^ces." — Cuv. Regne Anim. i. p. 428. 



while 



