BIEDS OF NORTH AND MIDDLE AMERICA. 301 



sometimes compressed and often somewhat widened and depressed 

 basally, extremely variable as to relative length (from decidedly 

 shorter than head to longer than head, neck, and body together), 

 usually straight or more or less (sometimes excessively) decurved, 

 rarely recurved tenninally; mandible with a more or less distinct 

 median lateral groove or sulcus; nostrils basal, lateral, broadly 

 operculate, but often completely hidden by dense frontal feather- 

 ing; tongue extremely long, slender, extensile, split terminally, each 

 lateral division with the outer edge curled upward and inward for 

 part of its length, forming, in effect, two parallel tubes ; " only one 

 carotid artery (the left) ; feet small and usually relatively weak, the 

 tarsus not longer than middle toe with claw; anterior toes all directed 

 forward, subequal in length, the hallux well developed (nearly as 

 large as anterior toes), the claws strongly curved and sharp; deep 

 plantar tendons not Coraciine but much as in Eurylaimidie (Desmo- 

 dactyli ^), the fi'ont tendon leading to the three anterior toes, the 

 hinder one to the hallux; wing much as in the Micropodii, the pri- 

 maries excessively developed and the secondaries correspondingly 

 reduced, the latter not longer than the first (innermost) primary and 

 only six to seven in number, the former ten in number, with the 

 outermost (tenth) longest or (rarely) equal to the ninth (in genra 

 Aithurus and 6'^oMma?iia) distmctly shorter than ninth; rectrices ten, 

 the tail excessivel}'^ variable m relative length, form, etc.;*^ young 

 nidicolous and gymnopsedic ; nest open above, variable as to fonn and 

 position but usually cup-shaped and attached to a twig, composed of 

 plant-downs or other soft materials, usually stuccoed exteriorly with 

 bits of moss, lichen, or fragments of bark and spiders' webs; eggs one 

 or (usually) two, broadly elliptical, immaculate white. 



Inhabitants exclusively of America, the ITunnnmg Birds constitute 

 not only the most charming element in the wonderfull}^ varied bird- 

 Hfe of the Western Hemisphere, but, also, without doubt, the most 

 remarkable grouj) of birds in the entire world. No other grouj) of 

 birds is so brilliant in plumage or so difYerent from all others in their 

 mode of flight and manner of feedmg. The general habits of Hum- 

 ming Birds are not dissimilar to those of birds in general. They 

 are both aerial and arboreal, but are unable to progress upon the 

 ground or any flat surface by means of their legs and feet alone. 

 They perch readily and frequently u})on trees or bushes, or may 



a The tongue of Trochilidte is described iu detail by Dr. F. A. Lucas in Proc. 

 U. S. Nat. Mus., xiv, 1891, 169-172, pi. iv, and Rep. U. S. Nat. Mus., 1892, 293, 294, 

 where the reader is referred for further information on the subject. 



b See Part I, p. 14. 



c More so than in any other group of birds. For a detailed account (»f variations 

 in the form of the tail, etc., in the Trochilidse see Rep. U. S. Nat. Mus., 1,S92, 294-301. 



