16 BRITISH BIRDS. 



FALCO GYRFALCO AND FALCO CANDICANS. 

 BROWN JER-FALCON and WHITE JER-FALCON. 



(PLATE 3.) 



There are two species of Jer-Falcons, very distinct from each other, and 

 having well-defined geographical ranges, but connected together by a series 

 of intermediate forms in the intermediate localities. It is not known that 

 these intermediate forms are produced by the interbreeding of the two 

 extremes ; but in the case of the form which inhabits Iceland there seems 

 to be evidence that some interbreeding does take place (see Ibis, 1862, 

 p. 47, footnote) . The synonymy of the two species and their most im- 

 portant intermediate forms is as follows : 



FALCO GYRFALCO. 

 BBOWN JER-FALCON. 



Falco gyrfalco, Linn. Syst. Nat. i. p. 130 (1766) ; et auctorum plurimorum 



Schlegel, Bonaparte, Naumann, Gould, {Sharpe), &c. 

 Falco sacer, Briss. apud Forst. Phil Trans. Roy. Soc. Ixii. p. 382 (1772). 

 Falco lanarius, Linn, apud Lath. Gen. Syn. Suppl. i. p. 282 (1787). 

 Falco sacer, var. j3, Gmel. Syst. Nat. i. p. 273 (1788, ex Forst.}. 

 Hierofalco gyrfalco (Linn.), Brehm, Journ. Orn. 1853, p. 266. 

 Falco norvegicus, Tristr. Ibis, 1859, p. 24 (ex Wolley's Sale Cat. nee Lath.} 

 Falco gyrfalco norwegicus, Schl. Mus. Pays-Bas, ii. Falcones, p. 12 (1862, nee Lath.). 

 Falco (Hierofalco) gyrfalco (Linn.), var. gyrfalco (Linn.), JRidgw. N. Amer. Birds, 



iii. p. 108 (1874). 

 Falco (Hierofalco) gyrfalco (Linn.), var. sacer (Forst.), Ridgw. N. Amer. Birds, iii. 



p. 115 (1874). 



FALCO GYRFALCO-CANDICANS. 



ICELAND JEB-FALCON. 



Accipiter falco islandicus, Briss. Orn. i. p. 336 (1760). 



Accipiter gyrfalco islandicus, Briss. Orn. i. p. 373 (1760). 



Falco islandus, Gmel. Syst. Nat. i. p. 271 (1788, ex Briinn. nee Lath.). 



Hierofalco islandus {Gmel), Sharpe, Cat. Birds Brit. Mus. i. p. 414 (1874, nee Lath.). 



FALCO CANDICANS-GYRFALCO. 



SOUTH-GBEENLAND JEB-FALCON. 



Falco rusticolus, Linn. Syst. Nat. i. p. 125 (1766). 



Falco fuscus, Faber, Faun. Groenl. p. 59 (1780). 



Falco arcticus, Holb. Zeltschr. Ges. Nat. iii. p. 426 (1854). 



Falco gyrfalco grcsnlandicus, Schl. Mus. Pays-Bas, ii. Falcones, p. 13 (1862). 



Falco holboelli, Sharpe, Proc. Zool. Soc. 1873, p. 415. 



Hierofalco holboelli (Sharpe), Sharpe, Cat. Birds Brit. Mus. i. p. 415, pi. xiii. (1874). 



