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difficulty in the matter, as hardly any two birds of the same general 
form and size could differ from each other more than the pure 
white Jerfalcon at the one end of the series does from the dark 
slate-coloured Jerfalcon at the other. The difference is so great 
that no one examining only the extremes of the series would 
hesitate for a moment to regard them as perfectly distinct species. 
But the comparison of great numbers of specimens brings to light 
the existence of many varieties of an intermediate character, which 
shade off into each other by almost imperceptible gradations of 
colouring, and seem to complete the connection between the two 
extremes. 
They that are unwilling to admit that there is really a passage 
from the one extreme to the other consider that the Jerfalcons 
may be divided into two groups, one that may be characterised as 
the light-coloured birds with dark markings, classified as Falco 
candicans, or the Greenland Falcon; and the other as the darker- 
coloured set with light markings, which is classified as Falco 
zslandus, or the Iceland Falcon. The Greenland Falcon, it is 
further said, may be readily distinguished at any age by the barring 
on the tail feathers being incomplete, and by the flank feathers 
being longitudinally striped instead of barred ; while, in the Iceland 
Falcon, the bars on the tail go right across each feather, and the 
flank feathers are invariably more or less barred. Other minor 
differences have been pointed out; but these, though readily 
enough detected by a trained eye, are not regarded as character- 
istics of sufficient constancy to have much importance as specific 
distinctions. 
A third section of the Jerfalcons is often distinguished as the 
Norway Falcon (Falco gyrfalco), or the Jerfalcon proper.* This is 
said to differ from the Iceland Falcon section in being somewhat 
smaller, darker in colour generally, and especially darker on the 
head, and in having the leg-plumes marked with transverse bars 
instead of the longitudinal stripes found in the other. This race, 
or sub-species, has not yet been recorded from any British locality. 
* See Schlegel’s Traité de Fauconnerie, and the paper by the late Mr. Hoy, 
Ann. Mag. Nat. Hist. vi. p. 108. 
