THE GYR-FALCONS. 
191 
the chestnut forms small spots and larger blotches. The eggs 
of the Merlin are often impossible to distinguish from those 
of the Hobby, and also from those of the Kestrel, though they 
seem never to vary to a pale form like so many of the Kestrel’s 
eggs do. Axis, i'45-i-6 inch; diam., i-i5-i-25. 
THE GYR-FALCONS. GENUS HIEROFALCO. 
Hierofalco, Cuvier, Rfegne Anim. i. p. 312 (1817). 
Type, H. cafidicans (Gm.). 
The Gyr-Falcons are giant Kestrels, and in the case of the 
Saker Gyr-Falcon {Hierofako saker) and Henderson’s Gyr-Fal- 
con {Hierofako hendersoni) the plumage is red and not unlike 
that of a Kestrel. Both the G) r-Falcons and Kestrels differ from 
the true Falcons (Fako), as typified by the Peregrine, in having 
the outer and inner toes about equal in length, whereas in 
every true Falcon the outer toe is longer than the inner one. 
The nostril in the Gyr-Falcon has always a central tubercle. 
The tarsus is finely reticulate in front, and is not double the 
length of the middle toe. Although the proportions of the 
toes are the same in the Gyr-Falcons and the Kestrels, the 
former have a somewhat less pointed wing, the distance be- 
tween the tips of the primaries and secondaries being equal to, 
or less than half of, the length of the tail. 
The true Gyr-Falcons are all birds of northern countries, 
and occur throughout the whole of the arctic and sub-arctic 
portions of the Old and New Worlds. The Kestrel-like Gyr- 
Falcons, H. saker, H. henderso?ii, and H. mexicatms, have a 
more southern habitat, and carry the range of the genus to 
Mexico in the New World, and to South-eastern Europe, 
Central Asia, and India in the Old World. 
I. THE GREENLAND GYR-FALCON. HIEROFALCO CANDICANS.* 
Fako candicans, Gmelin, Syst. Nat. i. p. 275 (1788) ; Newton, 
ed. Yarr. Brit. B. i. p. 36 (1871) ; Dresser, B. Eur. vi. p. 
21, pi. 368, 369(1876) ; Seebohm, Brit. B. i. p. 16(1883); 
Saunders, Man. Brit. B. p. 331 (1889); Lilford, Col. Fig. 
Brit. B. part xvii. (1891). 
* This species is called Falco islandus of Briinnich by the American 
ornithologists. The work, however, dates from 1764, and was therefore 
published before the 12th edition of Linnaeus in 1766, which is the recog- 
