Falco isabellinus, Swainson, An. Menag. p. 281, 1838. Tinnunculus sparverius, var. isabellinus, Ridgway, P. A. N. S. Phil. Dec. 1870, p. 149. Tinnunculus dominicensis (not of Gmel.!), Strickl. Orn. Syn. 1, 100, 1855 (in part only).
Sp. Char. Adult male (3,841, Prairie Mer Rouge, La., June, 1853; “J. F.”). Much like var. sparverius, but considerably darker in colors; plumbeous, crown dark with no rufous on vertex, nor darker shaft-lines. Rufous above more purplish-castaneous; cinereous of wings much darker; neck, jugulum, breast, and sides deep soft ochraceous, spots very few, and restricted to the sides. Wing, 7.00; tail, 4.70; tarsus, 1.25; middle toe, .90; culmen, .50. Wing-formula, 2, 3–4, 1.
Adult female (58,339, Jacksonville, Fla., June 10, 1869; C. J. Maynard). Differing from the female of var. sparverius in much darker colors, the rufous inclining to castaneous; bars broader, more sharply defined, pure black. Head above pure dark plumbeous, conspicuously different from the fine light ash of var. sparverius; vertex with touches only of rufous; markings beneath narrower, and nearly pure black, upon a deeper ochraceous ground. Wing, 7.20; tail, 4.50; tarsus, 1.20; middle toe, .83; culmen, .42. Primaries, 2, 3–1, 4.
Hab. North Atlantic and Caribbean coasts of South America, from Demerara northward, along the Gulf coast of Mexico and United States, through Texas and Louisiana to Florida.
This form, though quite different in its extreme condition from true sparverius, gradually grades into it. Few, if any, other specimens possess in so exaggerated a degree all the distinctive characters of those described, though all from the regions indicated agree in having darker colors and less rufous on the crown than specimens from the interior of North and Middle America.
A series of six adult male Sparrow Hawks from Florida, kindly loaned me for examination by Mr. J. A. Allen, includes three typical examples of this littoral race of subtropical continental America. They all agree in very deep dark colors, entire absence or merely slight indication of rufous on the vertex, and deeply ochraceous breast, with few markings. No. 14,499 (Miami, Fla., June 19, 1871) is remarkable for lacking entirely the black spots on wings and flanks, and bars on the back or longer scapulars; the three outer tail-feathers are almost wholly ashy-white, with about five transverse spots of black; the terminal white band is strongly tinged with ash; there is no trace of rufous on the crown. Wing, 6.80; tail, 4.80.
In the unspotted wings and sides and unbarred scapulars there is a resemblance in this specimen to F. leucophrys; which, however, has the ash very much lighter, the black “mustache” obsolete or wanting, the lower breast pure white instead of deep ochraceous; the under surface of the primaries plain white, with shallow dusky serrations along the shaft, instead of being heavily barred with dusky; always has a patch of rufous on the crown, a conspicuous frontal and superciliary stripe of white, and an entirely differently marked tail. In its much barred tail it also resembles the var. dominicensis to a slight extent; but the latter has the middle feathers also barred, and always has the scapulars, generally the entire dorsal region, heavily barred with black, and the wings, breast, and sides heavily spotted; the bill is larger, and there is always more or less rufous on the crown. The other two specimens are more like the average; they both have a mere trace of rufous on the crown, conspicuous bars on the scapulars, and spots on the wings. No. 5,188 (Hibernia, Fla., February 3, 1869) has only a few black specks on the flanks; the outer tail-feather ashy-white, with seven transverse black spots across inner web. Wing, 6.80; tail, 4.80. No. 5,373 (Hawkinsville, Fla., March 12, 1869) is similar, but has the flanks distinctly spotted with black, and the outer tail-feather with inner web plain pale rufous, with only the subterminal large black spot. Wing, 6.80; tail, 4.80.
A series of ten specimens (five males and five females) from Florida, kindly sent me for examination by Mr. C. J. Maynard, contains nothing but var. sparverius, with a few individuals inclining slightly toward var. isabellinus. The extreme are measurements of the series as follows: ♂. Wing, 6.60–6.90; tail, 4.50–4.70. ♀. Wing, 6.90–7.50; tail, 4.80–5.10. Four out of the five males have the deeply ochraceous unspotted breast of var. isabellinus, but all have more or less rufous on the crown, while the ash is of that light shade seen in var. sparverius. No. 476 has the upper tail-coverts mixed with feathers which are either wholly or partially ash, while the light bands of the outer tail-feathers are much tinged with the same; the scapulars are almost wholly fine ash, like the wings, and with heavy black bars. The females likewise all incline toward var. isabellinus, all having the dark bars above equal to or broader than the rufous ones. No. 6,441 is transversely spotted on the flanks with heavy black bars, and is scarcely distinguishable from females of var. dominicensis.
An adult male labelled as coming from Cuba, but probably from the southeastern United States, in the collection of the Boston Society, is so deeply colored as to strongly resemble the young male of T. sparveroides. There is not a trace of rufous on the crown, which is dark plumbeous; the lower parts are entirely deep rufous, except the throat, inclining more to ochraceous on the tibiæ and crissum; the whole lower surface entirely free from spots of any kind. The tail is very uniformly marked, being wholly rufous, except the usual narrow terminal band, or the outer web of lateral feathers, which are white,—the latter with a few indications of black spots near the shaft,—and the usual subterminal zone of black, which is very regular and continuous. Though in these respects so closely resembling the young ♂ of T. sparveroides, it may be distinguished from it by the sharp definition of the black markings on the side of the head and on the wing-coverts, and of the black bars on the inner webs of the primaries. We have every reason to doubt whether this specimen was actually collected in Cuba, since so many of the specimens in the Lafresnaye Collection are incorrectly labelled as regards locality.
A young ♂ from Georgia, in the same collection, is somewhat similar, but differs in the following respects. The rufous beneath is confined to the breast, sides, and abdomen, but is as deep (i.e. only a shade or two lighter than that on the back); the two outer pairs of tail-feathers are mostly ashy-white, with large spots of black.