BIRDS OF NORTH AND MIDDLE AMERICA 

 FALCO RUSTICOLUS OBSOLETUS Gmelin 



American Gtrfalcon 



633 



Adult (sexes alike) .—White phase: Extremely variable, but gener- 

 ally the birds fall into one of two types : 



a. Bar-tailed variety: Entire head, body, wings, and tail white, 

 usually with a faint creamy tinge, the top of the head with narrow 

 chaetura black shaft stripes, these broadening into tear-shaped 

 subtcrminal spots on the nape; interscapulars, scapulars, upper wing 

 coverts, back, rump, upper tail coverts, remiges, and rectrices broadly 

 barred with dark sepia to chaetura drab or even chaetura black, 

 only the subterminal dark band visible on the scapulars; interscapulars 

 and upper wing coverts, often somewhat broadly crescentic in shape; 



Figure 46. — Falco (Hierofalco) rusiicolus. 



the bars on the rump and upper tail coverts narrower; the primaries 

 with broad chaetm-a black apical areas very narrowly edged with 

 white, the dark bars disappearing on the inner webs, which are largely 

 immaculate white; the fourth primary (from outside) shorter than 

 the outermost one; median pair of rectrices with both webs crossed 

 by 9 to 11 dark bars (about 10 mm. broad), the other pairs with the 

 bars chiefly on the outer webs and becoming reduced in size to spots 

 and in number as well on the outermost tail feathers ; lores and cheeks 

 and auriculars with some fine dusky shaft streaks; chin, thi'oat, 

 breast, and middle of abdomen either immaculate white or with a 

 few small tear-shaped spots of chaetura di-ab on the breast and 

 abdomen; sides and flanks similar to breast and abdomen; thighs 

 either flecked or immaculate white; under tail coverts usually un- 



