16 BRITISH BIRDS. 



FALCO GYRFALCO and FALCO CANDICANS. 

 BROWN JER-FALCON and WHITE JER-FALCON. 



(Plate 3.) 



There are two species of Jer-FalconSj 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. 

 Beown Jer-Falcon. 



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



Schlegel, Bonaparte, Naumann, Ooitld, (Sharpe), &c. 

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

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

 Falco sacer, var. /3, Omel. Syst. Nat. i. p. 273 (1788, ex Forst.). 

 Hierofalco gyi'falco (Linn.), Brehm, Joiirn. Orn. 18-53, p. 266. 

 Falco norvegicus, Tristr. Ibis, 1859, p. 24 (ex Wolleys Sale Cat. nee Lath.) 

 Falco gyi'falco norwegicus, Sehl. Mus. Pays-Bas, ii. Falcones, p. 12 (1862, nee Lath.). 

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



iii. p. 108 (1874). 

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



p. 115 (1874). 



FALCO GYRFALCO-CANDICANS. 



ICBLAKD JbK-FaICON. 



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



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



Falco islanduf, Omel. Syst. Nat. i. p. 271 (1788, ex Briinn. nee Lath.). 



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



FALCO CANDICANS-GYRFALOO. 



SorTH-GnEEXLAXD Jek-Falcon. 



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



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



Falco arcticus, Holb. Zeitschr. Oes. Nat. iii. p. 426 (1854). 



Falco gyi'falco grosnlandicus, Sehl. Mus. Pays-Bas, ii. Falcones, p. 13 (1862). 



Falco holbrelli, Sharpe, Proc. Zool. Soe. 1873, p. 415. 



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



