PICARIAN BIRDS. 95 
saucer made of bark and feathers gummed by saliva to a branch, and 
is so small that the sitting bird entirely conceals it. Only one egg 
is laid. 
Family XII]. Trocuirivs. Humine-sirps. 
The Humming-birds or Hummers, so called from the sound often pro- 
duced by their vibrating wings, are exclusively a New World group, and 
must not be confounded with the Passerine group of Sunbirds (Nec- 
tariniide), which inhabit the Indian and African regions, and somewhat 
resemble them in outward appearance and habits. About five hundred 
species are known ; and of these the majority inhabit Central and South 
America, but some are found in the southern United States, and 
Selasphorus rufus (1318) migrates northwards in summer to Canada 
and even Alaska. Hustephanus galeritus (1213 a) frequents Tierra del 
Fuego even in snowy weather; while Oreotrochilus chimborazo (1804) 
and QO. pichincha (1803) are natives of the Andes of Ecuador, close to 
perpetual snow, at a height of 16,000 feet. All are very small birds, 
the largest being the Giant Humming-bird (Patagona gigas) (1808), 
about 94 inches long, while the smallest forms, such as Mellisuga 
minima (1826) and Chetocercus bombus (1326 a), are little larger than a 
bumble-bee and only measure 24 inches in length. 
The tongue of these birds is very peculiar, being slender, very long, 
and extensile. When drawn within the bill, the two branches of the 
hyoid bone which support its base curve upwards around the back of 
the skull, and then forward over the top of the head, as in the Wood- 
peckers (see preparation in Case). This arrangement allows the tongue 
to be suddenly protruded to a considerable distance and as quickly with- 
drawn. Unlike that of the Woodpeckers, the tongue is hollow and 
divided at the free end into two slender branches, each of which bears 
a thin membranous fringe on its outer margin. 
The plumage is usually of a brilliant metallic nature, produced by 
the prismatic surfaces of the feathers, and in many forms crests, ear- 
tufts, neck-frills, and other ornamental plumes add to the gorgeous 
effect. 
The wing-muscles are greatly developed, and enable the birds to 
sustain their untiring flight, which is more like that of a hawk-moth 
than a bird. The little creatures hover in front of a flower, suspended 
as it were in the air, their wings vibrating so rapidly that they merely 
appear like a grey film; an instant they remain poised, and then, with a 
flash of metallic colour, vanish with incredible speed. 
The length and shape of the bill varies greatly in the different genera ; 
some have the edges of the mandible strongly serrated towards the tip, 
while in others this serration is faint or absent. In the absence of 
[Case 62. | 
