108 NORTH AMERICAN BIRDS. 



1. Adult. Upper parts, excepting head and neck, with transverse 

 crescentic bars of dark pUunbeous ; lower parts immaculate, or 

 else without well-defined markings. Young. Upper parts with 

 longitudinal stripes of dark ]ilninbeous; lower parts usually con- 

 spicuously striped. Hab. Greenland (in the breeding-season) ; in 

 winter, occasionally wandering into the northern portions of 

 Europe and North America var. candicans. 



Lower tail-coverts always with markings. A tinge of ashy-blue more or 

 less prevalent above. Young dusky above. 



Head and neck above abruptly lighter than the back. Young plain 

 grayish-brown above, with conspicuous whitish borders to the feathers. 



2. Adult. Upper parts white, passing into bluish posteriorly ; 

 everywhere (except on head and neck) with sharply defined, 

 transverse (not crescentic, but continuous) bars of dark plumbeous. 

 Abdomen and flanks with transverse spots of the same. Young 

 without irregular light mottling to the plumage above, and with 

 broad longitudinal stripes beneath. Hab. Iceland and Southern 

 Greenland, in the breeding-season ; in winter, south into North- 

 eastern United States, and Northern Europe. . var. isla ndicus. 



Head and neck above abruptly darker than the back. Young (of var. 

 sace7') variegated grayish-brown above, without light borders to the 

 feathers. 



3. Adult. Top of the head streaked with whitish; back with 

 sharply defined, continuous, narrow transverse bars, of creamy- 

 white. Hab. Interior regions of Continental Arctic America 

 (Slave Lake, Yukon, and McKenzie River district) . . var. sacer. 



4. Adult. Top of head not streaked with Avhitish ; back without 

 sharply defined bars of the same. Hab. Continental Arctic Europe 

 (Scandinavia) and Siberia. Migrating south, in winter, to Bengal 

 (Hardwicke) . var. gyrfalru.^ 



b. Lower parts with dusky predominating, or wholly dusky. 



5. Adult. Almost entirely dusky, without well-defined markings 

 anywhere. Hab. Littoral regions of the Hudson Bay Territory 



and Labrador ........ var. labradora. 



2. F. lanarius. Wing, 11.50-16.00; tail, 6.60-9.50; cuhnen, .70-1.00; 

 tarsus, 1.90-2.40; middle toe, 1.65-2.00. Ground-color varying from pale 

 grayish-plumbeous to dai-k sepia-brown ; beneath white, with sparse markings, 

 these coalesced into a broken patch on the flanks. Adult. Above obscurely 

 barred transversely with pale ashy and brownish-dusky, the former prevailing 

 posteriorl)'^, the latter anteriorly ; a lighter nuchal band. Spots on the sides and 

 flanks transverse. Young. Above brown, varying from grayish-drab to dark 

 sepia, the feathers usually bordered with paler (rusty in youngest individuals) ; 

 markings beneath all longitudinal. 



a. Outer webs of tail-feathers with large well-defined light spots ; outer 

 webs of the primaries sometimes with light spots on the basal portion ; 



1 Falco gyrfalco, var. gyrfalco (Linn.). Fako gyrfalco, Linx. S. N. 1766, p. 130. ^Gmel. S. N. 

 275. — ScHLEG. Eev. Crit. II, Tr. de Fauc. X'b iii ; F- van Nederl. Vog. pis. iii and iv. — 

 Naum. Vog. pi. cccxci. Hierofalco gyrfalco, Schleg. Boxap. Rev. Zool. 1854, 535. — Newton, 

 Ootheca Wolleyana, I, 87, pi. c. F. gyrfalco norvegicus, Wolley. Falco gyrfalco norwegicus, 

 ScHLEG. Mus. Pays-Bas, 1862, 12. Falco candicans, var. 7, Blas. 



Wing, 13.00-14.50 ; tail, 9.30 ; culmen, .98 ; tarsus, 2.50 ; middle toe, 1.92. 



