Cathartidæ, Gray, 1842.—Huxley, P. Z. S. 1867, p. 463. Cathartinæ, Lafr. 1839. Sarcorhamphidæ, Gray, 1848. Gryphinæ, Reich. 1850.
The characters of this family have been given in sufficient detail (III, 1), so that a short diagnosis, showing its most readily observable peculiarities, will here be sufficient.
Char. Whole head, and sometimes the neck, naked; eyes prominent, and not shaded by a superciliary shield. Cere much elongated, much depressed anteriorly below the very arched culmen; nostrils longitudinal, horizontal, the two confluent or perforate. Middle toe very long, and the hind one much abbreviated. A web between the base of the inner and middle toes.
The family Vulturidæ,[94] as long recognized, included all the naked-headed, carrion-feeding Raptores of both the Old and the New World. The later researches of science, however, have shown the necessity of separating the Vultures of the latter continent from those of the former, and ranking them as a distinct family, while at the same time the Old World Vultures are found to be merely modified Falconidæ. The resemblance between the Cathartidæ and the vulturine Falconidæ is merely a superficial one of analogy, and not one of affinity. Being the scavengers of the countries they inhabit, the latter thus perform the same office in nature as the former, and for adaptation to a similar mode of life their external characters are modified to correspond. Close, however, as is the external resemblance between the two groups, their osteological structure and internal anatomy is entirely different.
The Cathartidæ differ from the Vulturinæ[95] as to their external structure in the following particulars, the osteological structure being entirely different in the two groups, the latter being like the Falconidæ in all the characters which separate the latter family from the Cathartidæ.
Cathartidæ. Nostrils horizontal, perforate; a well-developed web between the inner and middle toes, at the base.
Vulturinæ. Nostrils vertical, not perforate; no trace of web between inner and middle toes.
In habits, the Cathartidæ resemble the vulturine Falconidæ of the Old World. “They lack the strength and spirit of typical Raptores, and rarely attack animals capable of offering resistance; they are voracious and indiscriminate gormandizers of carrion and animal refuse of all sorts,—efficient and almost indispensable scavengers in the warm countries where they abound. They are uncleanly in their mode of feeding; the nature of their food renders them ill-scented, and when disturbed they eject the fetid contents of the crop. Although not truly gregarious, they assemble in multitudes where food is plenty, and some species breed in communities. When gorged, they appear heavy and indisposed to exertion, usually passing the period of digestion motionless, in a listless attitude, with their wings half spread. But they spend most of the time on wing, circling high in the air; their flight is easy and graceful in the extreme, and capable of being indefinitely protracted. On the ground, they habitually walk instead of progressing by leaps. Possessing no vocal apparatus, the Vultures are almost mute, emitting only a weak hissing sound.” (Coues.)
The Cathartidæ all belong to the tropical and warm temperate portions of the continent, only one species (Rhinogryphus aura) extending its range as far as the border of the colder regions. The famous Condor (Sarcorhamphus gryphus) of the Andes and the equally large California species (Pseudogryphus californianus) are among the largest birds of flight in the world, being exceeded in size by none, and rivalled but by one or two of the Vultures of the Eastern Hemisphere.
The following diagnoses based upon the external structure are sufficient to characterize the very well-marked genera and subgenera of this family. The distinctive osteological characters which accompany these external features afford still more decided differences, and are illustrated by the figures.