BIRDS 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 terminally; 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;7 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 Eurylaimide (Desmo- 
dactyli >), the front 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 Gonermost) 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 Goldmania) distinctly shorter than ninth; rectrices ten, 
the tail excessively variable in relative length, form, etc.;*° young 
nidicolous and gymnopedic; nest open above, variable as to form 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 Humming Birds constitute 
not only the most charming element in the wonderfully varied bird- 
life of the Western Hemisphere, but, also, without doubt, the most 
remarkable group of birds in the entire world. No other group of 
birds is so brilliant in plumage or so different from all others in their 
mode of flight and manner of feeding. The general habits of Hum- 
ming Birds are not dissimilar to those of birds in general. They 
are both aérial 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 upon trees or bushes, or may 
«The tongue of Trochilide is described in detail by Dr. F. A. Lucas in Proc. 
U. 8. Nat. Mus., xiv, 1891, 169-172, pl. iv, and Rep. U. 8. Nat. Mus., 1892, 293, 294, 
where the reader is referred for further information on the subject. 
b See Part I, p. 14. 
¢ More so than in any other group of birds. For a detailed account of variations 
in the form of the tail, etc., in the Trochilidz see’ Rep. U. 8. Nat. Mus., 1892, 294-301. 
