FALCONID2E DIURNAL RAPTORES. 429 



3. JEsalon. Size small (wing never more than 9 inches). Sexes very different in 



adult plumage, the young of both sexes resembling the adult female. 

 &. Basal joint of toes covered with transverse scutellae. Tarsus longer than middle 



toe. 



4. Tinnnnculus. Size small (wing never more than 8 inches in the American 

 species). Sexes very different at all ages, but not differing according to age.* 

 Large transverse scutellae of feet interrupted at lower extremity of tarsus and 

 extreme base of toes. Tarsus much longer than middle toe. Bill small, the cere 

 on the top less than one fourth the culmen. 



6. Bhynchofalco. Size medium (wing more than 9 inches). Sexes alike in color, 

 and young not essentially different from adults. Large scutellas of feet unin- 

 terrupted at base of toes. Tarsus but little longer than middle toe. Bill very 

 robust, the cere on top about one third the culmen. (Trooical. north to Texas.) 



SUBGENUS Hierofalco CUYIER. 



Hierofalco Cuv. Reg. An. 1817, 312. Type, Falco candicans GMEL.,=JF'.tsZandusBBUNN. 

 Gennaia KAUP. Isis, 1847, 69. Type, Falco jugger GBAT. 



Synopsis of North American Species. 



. F. gyrfalco. Feathering of the tarsus extending around on to the posterior face, 

 where the narrow naked strip is nearly or auite concealed. Male. Wing, 13.00-15.80; 

 tail, 7.50-10.00. Female. Wing, 15.75-17.00; tail, 9.50-11.50. Colors extremely variable, 

 the extremes being bluish or brownish gray barred or striped with dusky on the 

 upper parts, and uniform dark sooty slate, with few or no light markings. 

 F. mexicanus. Feathering of the tarsus confined almost wholly to the anterior face, 

 the posterior face entirely naked. Male. Wing, 11.80-12.50; tail, 6.40-8.00. Female. 

 Wing, 13.25-14.30; tail, 8.00-9.00. Adult male. Above light brown, barred anteriorly 

 with pale fulvous and posteriorly with pale bluish gray; top of head grayish brown, 

 streaked with dusky. Adult female. Above brown, without distinct bars, but 

 feathers bordered with paler rusty brown. Young. Above brown, feathers distinctly 

 margined with* light rusty ; beneath creamy white, the axillars and broken flank- 

 patch dusky brown; chest, etc., streaked with dark brown. 



Falco mexicanus Schleg. 



PRAIRIE FALCON. 



Popular synonym. American Lanner Falcon. 

 Falco mexicanus "LIGHT." SCHLEG. Abh. Geb. Zool. 1841, 15,-CouES, Key. 1872, 213; 



Check List, 1874, No. 342; 2d ed. 1882, No. 502. 

 Falco polyagrus (part) CASS. Proc. Phil. Acad. vi, 1854. 450; Illustr. B. Cal. etc. 1853. 88. 



pi. 16 (light fig.) ; in Baird's B. N. Am. 1858. 12.-BAIED, Cat. N. Am. B. 1859, No. 10. 

 Falco lanarius var. polyagrus B. B. & R. Hist N. Am. B. iii. 1874. 123. 

 Hierofalco mexicanus polyagrus RIDGW. Nona. N. Am. B. 1881, No. 412. 

 HAB. Western United States and table-lands of Mexico; north to Washington Ter- 

 ritory and Dakota, east to Illinois (prairie districts), Indian Territory, etc. 



In the European Kestril (F. tinnunculus Linn.) and its Old World allies, the young 

 male is said to resemble the adult female in coloration. 



