Part 28

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. 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. No lighter nuchal band. Young. Markings of the lower surface longitudinal, the upper parts without transverse bars (except on the tail).

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.

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.

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.