Polyborus auduboni.
This well-marked genus contains but a single species, the P. tharus, Mol., which extends its range over the whole of tropical and subtropical America, exclusive of some of the West India Islands. North and south of the Isthmus it is modified into geographical races, the southern of which is var. tharus, Mol., and the northern var. auduboni, Cass.
The closely related genera Phalcobænas, Milvago, Ibycter, and Daptrius are peculiar to South America and the southern portion of Middle America, most of them being represented by two or more species. They all form a well-marked and peculiarly American group, for which I shall retain Schlegel’s term Polybori.
Their habits are quite different in many respects from those of other Falconidæ, for they combine in many respects the habits of the gallinaceous birds and those of the Vultures. They are terrestrial, running and walking gracefully, with the exception of the species of Ibycter and Daptrius, which are more arboreal than the others, and are said also to feed chiefly upon insects, instead of carrion.
Species and Races.
P. tharus. Wing, 14.50–17.70; tail, 10.00–11.00; culmen, 1.20–1.48; tarsus, 3.20–4.20; middle toe, 1.75–2.30.
Adult. Forehead, crown, occiput, back, rump, abdomen, sides, and tibiæ, and terminal zone of the tail, dull black. Neck, breast, tail-coverts, and tail, dingy whitish. Interscapulars, breast, and tail with transverse dusky bars.
Young. Blackish areas replaced by dull brown; region of the transverse bars marked, instead, with longitudinal stripes.
Adult. Whole body, with middle wing-coverts, variegated with transverse bars of black and white; tail-coverts barred. Terminal zone of the tail about 2.00 wide. Young. Longitudinal stripes over the whole head and body, except throat, cheeks, and tail-coverts; tail-coverts transversely barred. Hab. South America … var. tharus.[67]