Family CAPRIMULGIDÆ.—The Goatsuckers.
Char. Bill very short; the gape enormously long and wide, opening to beneath or behind the eyes. Culmen variable. Toes connected by a movable skin; secondaries lengthened; plumage soft, sometimes very full and loose, as in the Owls.
The preceding diagnosis in connection with that of the order will suffice to separate the Caprimulgidæ from their allies. Their closest relatives are the Cypselidæ, next to which perhaps may be reckoned the Trochilidæ.
In defining the subdivisions of this family, we make use of an excellent monograph of the American species by Dr. Sclater, in Proceedings of the Zoölogical Society, London, 1866, 123. He establishes three subfamilies as follows:—
I. Podarginæ. Claw of middle toe not pectinated; outer toe with five phalanges. Sternum with two pairs of posterior fissures.
Outer pair of posterior sternal fissures much deeper than inner pair; tarsus long and naked. Eggs colorless. Podargus, Batrachostomus, Ægotheles, Old World.
Outer pair of posterior fissures much deeper than inner pair; tarsus extremely short and feathered. Nyctibius, New World.
II. Steatornithinæ. Claw of middle toe not pectinated; outer toe with five phalanges. Sternum with one pair of shallow posterior fissures. Eggs colorless. Steatornis, New World.
III. Caprimulginæ. Claw of middle toe pectinated; outer toe with four phalanges only. Sternum with one pair of shallow posterior fissures. Eggs colored (colorless in Antrostomus nuttalli, Baird).