646 BULLETIN 5 0, UNITED STATES NATIONAL MUSEUM 



Falco (Hierofalco) labradorus Ridoway, Proc. Acad. Nat. Sci. Philadelphia, 1870, 

 140. 



Falco (Hierofalco) sacer c. var. labradora Ridgway, Proc. Boston Soc. Nat. Hist., 

 xvi, 1873, 44. 



Falco (Hierofalco) gyrfalco var. labradora Ridgway, in Baird, Brewer, and Ridg- 

 way, Hist. North Amer. Birds, iii, 1874, 108, 117 (Rigolet, Fort Nascopie, 

 Labrador; plum.). 



Falco labradorus Dresser, Proc. Zool. Soc. London, 1875, 115 (Fort Nascopie, 

 Labrador; crit.); Orn. Misc., i, 1876, 185 (Fort Nascopie, Labrador; crit.). 



Hierofalco gyrfalco var. labradora Boucard, Cat., 1876, 87, No. 2465 ("N. Amer- 

 ica"). 



Falco sacer var. labradora Cory, Bull. Nuttall Orn. Club, ii, 1877, 27 (Breels 

 Island, Mass.). 



Falco sacer labradorus Vennor, Forest and Stream, xii, 1879, 406 (Montreal, 

 Canada). 



Falco rusticolus labradora Bird, Ibis, 1941, 132, in text (crit.). 



Hierofalco labradora Brewer, Proc. Boston Soc. Nat. Hist., xvii, 1875, 444. — 

 GuRNEY, List Diurn. Birds Prey, 1882, 111.— Hantszch, Can. Field Nat., 

 xlii, 1928, 30 (ne. Labrador; trans.; colors). 



Hierofalco labradorus Heine and Reichenow, Nom. Mus. Hein. Orn., 1886, 263 

 (Labrador). — Menzbier and Sushkin, Ibis, 1903, 242 (plum.). 



Falco arcticus Holboell, Zeitschr. Ges. Naturw., iii, 1854, 426. — Blasitis, Nau- 

 mannia, 1857, 238; Nachtrag Naum. Vog. Deutschl., 1860, 19 (not pi. 390, 

 fig. 2).— Palmer, Condor, xxx, 1928, 282, in text. 



Falco dawsonis Hall, Can. Nat. and GeoL, vii, 1862, 62 (Montreal, Canada; 

 Juvenal). 



Falco holboelli Skarpe, Proc. Zool. Soc. London, 1873, 415 (s. Greenland). 



Falco rusticolus holboelli Schi0ler, Danmarks Fugle, iii, 1931, 361. — Bird, Ibis, 

 1941, 132, in text (crit.). 



Hierofalco holboelli Sharpe, Cat. Birds Brit. Mus., i, 1874, pi. 13 (adult and 

 young).— GuRNEY, Ibis, 1882, 587-591 (crit.).— Boucard, Cat., 1876, 87, 

 No. 2462 (Greenland). — Palmer, Condor, xxx, 1928, 282, in text (patro- 

 nymics). 



Hierofalco islandus subspecies a. holboelli Gurney, List Diurn. Birds Prey, 1884, 

 111. 



FALCO RUSTICOLUS URALENSIS (Severlzov and Menzbier) 



Siberian Gyrfalcon 



Adult (sexes alike). — White phase: Both barred and plain-tailed 

 varieties present, indistinguishable from corresponding plumages of 

 Falco rusticolus ohsoletus except that the fourth primary (from the 

 outside) is as long as, or longer than, the outermost one, while in 

 ohsoletus it is shorter than the outermost one. 



Adult. — Gray phase: Differs from that of Falco rusticolus ohsoletus 

 only in the same character as do the birds of the white phase. 



Juvenal. — White phase: Both barred and plain-tailed varieties 

 differ from those of Falco rusticolus ohsoletus only in the relative length 

 of the fourth and the outermost primary, as in the adults. 



Juvenal. — Gray phase: Similar to the pale variety of the gray 

 phase of Falco rusticolus ohsoletus, but with the fourth primary equal 



