b. Inner webs of primaries white, merely serrated along the shaft with dusky; “mustache” obsolete or wanting; a conspicuous superciliary stripe of white.
2. T. leucophrys.[62] Similar to sparverius, except as characterized above. Hab. Cuba and Hayti.
B. Back rufous only in the ♀. Lower parts deep ferruginous-rufous; front and auriculars dusky.
3. T. sparveroides.[63] ♂. Above, except the tail, entirely dark plumbeous, with a blackish nuchal collar; primaries and edges and subterminal portion of tail-feathers, black. Beneath deep rufous (like the back of sparverius and leucophrys), with a wash of plumbeous across the jugulum; throat grayish-white. Inner webs of primaries slaty, with transverse cloudings of darker. ♀. Differing from that of the above species in dark rufous lower parts and dusky, mottled inner webs of primaries. Second and third quills longest; first shorter than or equal to fourth. Hab. Cuba (only?).
The distinguishing characters of F. sparverius having been given in the foregoing synopsis, I will here consider this species in regard to the modifications it experiences in the different regions of its geographical distribution.
The whole of continental America, from the Arctic regions to almost the extreme of South America, and from ocean to ocean, is inhabited, so far as known, by but this one species of Tinnunculus. But in different portions of this vast extent of territory the species experiences modifications under the influence of certain climatic and other local conditions, which are here characterized as geographical races; these, let me say, present their distinctive characteristics with great uniformity and constancy, although the differences from the typical or restricted sparverius are not very great. The F. sparverius as restricted, or what is more properly termed var. sparverius, inhabits the whole of North and Middle America (both coasts included, except those of the Gulf of Mexico and Caribbean Sea), south to the Isthmus of Panama. Throughout this whole region it is everywhere nearly the same bird. This variety appears to represent the species in its greatest purity, being a sort of central form from which the others radiate. The most typical examples of the var. sparverius are the specimens in the large series from the elevated regions or plateau of Mexico and Guatemala. In these the rufous of the crown is most extended (in none is it at all restricted), and the ashy portions are of the finest or bluest and lightest tint.
All specimens, of quite a large series, from the peninsula of Lower California, are considerably smaller than any others, the smallest (1,693 ♂ ad. San José; J. Xantus) measuring, wing, 6.50; tail, 4.20, and tarsus, 1.30; the dwarfed size of these, however, is their only distinguishing feature. Two specimens (50,199, ♂, Cape Florida, and 10,345, ♀, Indian Key) from Florida differ from others in the unusual development of the bill, which toward the end is more suddenly curved, and the point considerably lengthened; these specimens have, also, only a tinge of rufous on the crown, thus showing a proximity to the var. isabellinus. The large bill, however, is no more than would be looked for in specimens from that region.
Along the Gulf border of the United States, and the Caribbean and North Atlantic coasts of South America (probably the whole Atlantic coast of tropical and subtropical America), the true sparverius is changed into what Swainson has called “Falco isabellinus,” which differs from the former only in having the cinereous of the crown and wings considerably darker (as well as less bluish), approaching plumbeous; the rufous of the crown is totally absent, or only present in faint touches; the lower parts are of a deeper ochraceous, and the black spots on the breast and sides sparse.
Allied to the last in tints of coloration, and apparently a direct offshoot from it, is the dominicensis of Gmelin (based upon description by Brisson), which inhabits the Lesser Antilles, from Trinidad northward to Porto Rico. Although I consider this (var. dominicensis) as a modified form of the var. isabellinus, yet it is the one of all the varieties referrible to sparverius which deviates most widely from the typical or original style. The characters of this are, tints those of var. isabellinus, but, in addition, the tail has numerous more or less complete black bands, while those of the back and scapulars are very broad and numerous; also, the crown has a decided rufous patch; the bill, too, is larger than in any other American member of the genus. A style of considerable uniformity spreads over the whole of South America, including both coasts, from Bogota to the Parana, excepting the northeastern coast region, before mentioned as inhabited by the var. isabellinus. It differs from all the other styles, except the cinnamominus of Chile, in having the lower parts continuously dull white, any ochraceous tinge being scarcely perceptible; there is seldom a trace of rufous on the crown, which has the light bluish tint seen in var. sparverius, and the black zone of the tail is scarcely more than half as wide as in the northern races. In size, also, it somewhat exceeds the others. Swainson named this “Falco gracilis”; but the F. (Tinnunculus) gracilis of Lesson being a different species, and the name as applied to it of prior date, I have bestowed upon the present bird the name var. australis.