Secondaries only six.
Bill tenuirostral, longer than head, nearly cylindrical. Gape
constricted. Tongue filiform, extensile, bi-tubular. Wings long
in terminal portion, abbreviated proximally, acute. Plumage
compact, of metallic sheen. Size smallest of all birds.
(Humming-Birds.) … _Trochilidæ._
Secondaries more than six.
Feet syndactyle by connation of outer and middle toes.
Outer toe much longer than the inner, united for half its
length with the middle, forming a broad sole. Tibiæ naked
below. Bill longer than head, straight, acute, with hard
cutting edges and ample rictus. Tongue rudimentary, fixed.
Wings pointed, much longer than the short square tail.
Tail-feathers twelve. Plumage compact, oily. (Kingfishers.) …
_Alcedinidæ._
Feet zygodactyle[18] by reversion of outer or fourth toe.
Not scansorial; tail of eight or ten long soft feathers. Bill
with decurved tip, not fitted for hammering; rictus ample.
Tongue not extensile nor vermiform nor barbed. Salivary
glands and hyoidean apparatus not peculiar. No nasal tufts of
feathers. Arboreal and terrestrial. (Cuckoos.) … _Cuculidæ._
Highly scansorial; tail of twelve rigid acuminate feathers,
whereof the outer pair are short and spurious, concealed
between bases of next two pairs. Bill stout, straight, with
the tip truncate or acute, not decurved,—an efficient chisel
for hammering and boring wood. Tongue vermiform,
extensile,[19] and barbed. Salivary glands large; hyoidean
apparatus peculiar. Nasal tufts usually present. Arboreal.
(Woodpeckers.) … _Picidæ._
Feet neither syndactyle nor zygodactyle.
Feet semipalmate, of normal ratio of phalanges. Anterior toes
connected at base by movable webbing. Hind toe very small,
elevated, semilateral. Middle toe produced, its large claw
pectinate. Bill fissirostral, with very small, triangular,
depressed horny part and immense rictus, reaching below the
eyes, furnished with bristles. Rather large. Plumage soft and
lax, much variegated … _Caprimulgidæ_.
Feet scarcely or not semipalmate, of frequently abnormal
ratio of phalanges (middle or outer toe, or both, with fewer
joints than usual among birds). Hallux very small, elevated,
frequently lateral or versatile. Middle toe not produced nor
its claw pectinate. Bill much as in the last, but rictus
unbristled. Small. Plumage compact, of few simple subdued
colors … _Cypselidæ_.