_Hierofalco_, CUVIER, 1817. (Type, _Falco gyrfalco_, LINN.)
_Jerafalco_, BOIE, 1822; KAUP, 1851. (Same type.)
_Gennaia_, KAUP, 1847. (Type, _Falco jugger_, GRAY.)
Species and Races.
=1.= =F. gyrfalco.= Wing, 13.00–17.00; tail, 8.50–11.50; culmen,
.85–1.05; tarsus, 2.10–3.00; middle toe, 1.80–2.25.[45] Ground-color
varying from entirely pure white to wholly dusky, but generally bluish
(in adult) or grayish-brown (in young) above, and white beneath.
_Adult._ All the markings transverse.[46] No lighter nuchal band.
_Young._ Markings of the lower surface longitudinal, the upper parts
without transverse bars (except on the tail[47]).
_a._ Lower parts with white predominating, or wholly white.
Lower tail-coverts never with markings. No tinge of blue anywhere
on the plumage, the ground-color of which is entirely pure white
at all ages.
1. _Adult._ Upper parts, excepting head and neck, with
transverse crescentic bars of dark plumbeous; lower parts
immaculate, or else without well-defined markings. _Young._
Upper parts with longitudinal stripes of dark plumbeous; lower
parts usually conspicuously 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 Northeastern United States, and Northern
Europe …
var. _islandicus_.
Head and neck above abruptly darker than the back. Young (of
var. _sacer_) 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 whitish; back
without sharply defined bars of the same. _Hab._ Continental
Arctic Europe (Scandinavia) and Siberia. Migrating south, in
winter, to Bengal (Hardwicke) …
var. _gyrfalco_.[48]
_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; culmen,
.70–1.00; tarsus, 1.90–2.40; middle toe, 1.65–2.00. Ground-color
varying from pale grayish-plumbeous to dark 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 posteriorly, 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; secondaries without distinct spots on the outer webs.
Lower tail-coverts immaculate.
Wing, 13.65–16.00; tail, 8.40–9.50; culmen, .85–1.00; tarsus,
1.95–2.15; middle toe, 1.85–1.95. Top of the head white, with
narrow streaks of dark brown. _Hab._ Central and Eastern Europe,
Western Asia, and adjoining portions of Africa …
var. _lanarius_.[49]
_b._ Outer webs of tail-feathers without distinct light spots, or
without any at all; outer webs of primaries with no trace of spots;
secondaries with light spots on outer webs. Lower tail-coverts
sparsely spotted.
Wing, 12.00–14.25; tail, 7.60–9.00; culmen, .75–.90; tarsus,
2.15–2.40; middle toe, 1.70–2.00. Top of head brown, with narrow
black streaks. _Adult._ Above with obscure transverse spots of
bluish. _Young._ Above with feathers bordered with rusty …
var. _polyagrus_.
Wing, 11.50; tail, 6.60; culmen, .70; tarsus, 1.90; middle toe,
1.65. Above uniform dark brown, with a faint plumbeous cast, the
feathers without trace of light or rusty edges; outer web of
tail-feathers without trace of light spots. _Hab._ Mexico …
var. _mexicanus_.[50]
Wing, 13.60–14.30; tail, 8.25–9.00; culmen, .80–.87; tarsus,
1.85–1.90; middle toe, 1.85–1.90. Colors similar to the last;
entire auriculars white; mustache narrow and conspicuous. _Hab._
Southern Asia …
var. _jugger_.[51]
The only point of difference in the external anatomy between the Lanner
Falcons and Gerfalcons consists in the different degree of feathering on
the upper part of the tarsus; this is much denser and extends farther
down and more around the posterior face in the Gerfalcons, but they,
being inhabitants of a very northern latitude, need this protection
against the rigor of the climate. These slight specific differences
are illustrated by the figures on page 1430. The same difference is
observable in many birds whose habitat extends through a great range of
latitude, as, for instance, the _Pediocætes phasianellus_, the northern
race of which has the feathers covering the base of the toes so long as
to reach beyond the claws and nearly conceal them, while in the southern
form (var. _columbianus_) the toes are almost completely naked.
My determination of the number and character of the geographical races
of _F. gyrfalco_ is the result of a very careful critical examination of
over sixty specimens, aided by the important conclusions of Mr. Hancock
(Annals and Magazine of Natural History, 2d ser., XIII, 110; London,
1834), Schlegel (_Falcones_, Muséum d’Histoire Naturelle des Pays-Bas,
1862), Pelzeln (Uebersicht der Geier und Falken der Kaiserlichen
ornithologischen Sammlung, April, 1863), and Alfred Newton (History of
British Birds, revised ed., part 1, June, 1871, pp. 36–52, and Proc.
Acad. Nat. Sc. Philadelphia, July, 1871, pp. 94, 95), in their important
papers bearing upon this subject, which, though they each express the
peculiar individual views of the writer, together clear up pretty
satisfactorily the problem of the number, character, and habitats of the
several races, as well as the different phases of variation to which
each is subject.
[Illustration: =43139=, ♀. ½
_Falco sacer._]
[Illustration: =43139=, ♀. ¼]
[Illustration: =5482=, ♀. ½
_Falco polyagrus._]
[Illustration: =43139=, ♀. ½]
[Illustration: =5482=, ♀. ½]
In studying the _F. lanarius_, I have experienced most discouraging
difficulties from the want of sufficient series of the Old World races,
and from the unsatisfactory character of most descriptions and figures
of them, besides being much perplexed by the confusion of their synonymy
by different authors. In consequence of this, my diagnoses of the four
races of which alone I have seen examples may be very unsatisfactory as
regards the characters by which they may be most readily distinguished.
Having seen the adult of only a single one of these four races, I am
therefore compelled to base my differential characters upon the immature
stages.
In addition to the four races of _F. lanarius_ characterized above,
there are several geographical forms belonging to the Old World, chiefly
intertropical Asia and Africa. These are the var. _babylonicus_, Scl.
and Irby, (Gray’s Hand List, I, p. 20, No. 173,) of Southeastern
Europe and Western Asia; var. _barbarus_, L. (Gray’s Hand List, p. 20,
No. 174), of Northern Africa; and var. _tanypterus_, Licht. (Gray’s
Hand List, No. 175), of both the preceding regions, which Mr. Gurney
writes me “is simply the intertropical race of _F. lanarius_, from
which it only differs in being of a darker shade throughout.” The _F.
saker_, Schleg. (Gray’s Hand List, No. 176), seems, to judge from the
descriptions and figures which I have seen, to be also merely a form of
the same species, but I have seen no specimens of it.
Falco (Hierofalco) gyrfalco, LINN.
Var. =candicans=, GMELIN.