FALCON ID.E — THE FALCONS. 108 



Family FALCONIDiE. — The Falcons. 



CiiAU. EvL's (lircctL'il laterally, and oyuliils provii!'?(l witli lashes. Toes invariably 

 nukeil, ami tar.si'.s usually naked and soutoUate (feallici'cd only in Aqidlfi and Archilii'teo). 

 Outer toj not reversible (o.xeept in Pandiori). Head never with ear-tufts, and never 

 wholly naked (exeept in tlit; Vidturiiur, of the Old World). 



The aluivo characters are about tlie only readily observable points in the 

 external a- a*-oniy in which the Fcdvonidd' difler strikingly from tlie Sfrif/i(fa: 

 and CafhiirtuJa', and may serve to distinguish the birds of this family from 

 those of the two others. The osteological characters, however, as expressed 

 on page 1;?28, are more decided and important in a taxonomic point of 

 view, and serve to separate the Hawk family as a well-dehned group. 



In the following treatment of the Xovth American Falronidw, I confine 

 that part relating to the systematic arrangement strictly to tiie s])ecies 

 embraced within the province of our work, for the reason that in a forth- 

 coming nionogra])h of all the American species 1 hope to ])reseut a system- 

 atic classification based upon the species (jf the whole world. All jirelimi- 

 nary details regarding the general characteristics and distinctive peculiarities 

 of the family, as well as all discussions and generalizations upon the subject, 

 will therefore be omitted here. 



The following synopsis of the North American genera is intended as an 

 artificial arrangement which may enable the student to identify, by simple 

 and readily understood characters, the forms belonging to this country.* 



Genera. 



A. Nasal bone.'s almost eonipletoly os.'sified. the nostril being a .ssmall orifice, with 

 a conspicuous central bony tubercle ; its form nearly or quite circular, or linear 

 and oblique (in Poli/born.i), with its upper end the ])osterior one . . . Falconincn. 



1. Falco. Nostril cireidar. Commissure Avith a prominent tooth 

 and notch ; lower mandible abruptly truncate<l and notched. 

 Primaries stiff and hard, and more or less pointed, the first to the 

 second lon.sjest, and the outer one or two with their inner webs 

 cut, the angular emargination being near the end of the (piill. 

 Middle too much more than half as long as the tarsus; claws 

 strongly curved, very acute. 



2. Polyborus. Nostril linear, oblique, the upper end the posterior 

 one ; commissure without prominent tooth nor notch ; lower mandi- 

 ble not distinctly truncated or notched. Primaries soft, obtuse, 

 the third longest, and the outer four or five with their inner webs 

 cut, the shallow sinuation being toward the middle of the quill. 

 Middle toe less than half the tarsus ; claws weakly curved, very 

 obtuse. Face and cheeks naked, and si;antily haired. 



1 As in tlie case of the S/riijiilo; my detenninntioiis of tlie North American species of Fiil- 

 conidir were furnislica, according to ie(|uest, to Dr. Coues, for use in his " Key to North American 

 Birds." (R. R.) 



