Order
Accipitriformes
Family
Accipitridae
Genus
Pseudastur
 
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Version 1.0

This is a historic version of this account.  Current version

SPECIES

White Hawk Pseudastur albicollis

Brian Magnier and Thomas S. Schulenberg
Version: 1.0 — Published January 25, 2013

Appearance

Distinguishing Characteristics

The adult White Hawk ranges from 47-51 cm in length, with very broad wings. There are four subspecies; generally, the amount of black in the plumage increases from north to south. The northernmost subspecies, ghiesbreghti, is almost completely white, while the most southernmost subspecies, nominate albicollis, has extensive black on the back and shoulders. All subspecies, however, have white underparts, and a white or mostly white head. The tail is relatively short. The pattern of the tail also varies geographically, from mostly white with a subterminal black band in northern populations, to mostly black with a white base and a white tip in southern populations. The bill is black and hooked, and the tarsi are yellow. Sexes of White Hawk are similar in appearance, but, as is typical of hawks in general, females are larger and heavier than males. Immatures have black spotting on the upperparts and dark streaking below.

Similar Species

There are no similar species within the Central American range of White Hawk; adult King Vulture (Sarcoramphus papa) also has a white body, but easily is distinguished by the entirely black remiges, short black tail, and multicolored bare skin of the head and neck. There is no geographic overlap with Gray-backed Hawk (Pseudastur occidentalis) of western Ecuador and northwestern Peru; Gray-backed Hawk also has extensive dusky streaking on the crown and nape.

East of the Andes, White Hawk is distinguished from two other white hawks, Black-faced Hawk (Leucopternis melanops) and White-browed Hawk (Leucopternis kuhli), by its larger size, gray cere, and different tail pattern; White-browed Hawk also has a mostly gray crown and nape. Additionally, the species of Leucopternis do not soar.

Laughing Falcon (Herpetotheres cachinnans) also has light plumage, but is considerably smaller, is brown above, has a broad black mask, and overall is much slimmer, with a long tail.

Detailed Description

The following description refers to nominate albicollis, and is based on Blake (1977) and Ferguson-Lees and Christie (2001); see also Geographic Variation:

Adult: Sexes similar in appearance (but differ in size; see Measurements). Head white, nape variably streaked with black. Upper back black, variably spotted with white; lower back and rump white. Upper surface of wings black, with scattered white spots on coverts, and narrow white tips to scapulars, tertials, secondaries, and inner primaries; undersurface of remiges basally white to pale gray, the inner webs narrowly barred with dusky. Tail primarily black, with white base and narrower white tip.

Immature: Similar to adult, but "black of wings more extensive, and with narrow black shaft streaks on crown" (Blake 1977).

Molts

In general, members of Accipitridae follow a simple basic molt system. The molting system (timing and presence/absence of a prenuptial molt) of the White Hawk has not been described.

Bare Parts

Iris: brown in albicollis (Blake 1977), light yellow green in costaricensis (Robbins et al. 1985) and yellow in ghiesbreghti (Ridgway and Friedmann 1950, although Howell and Webb 1995 give the iris color of this subspecies as brown). Bare orbital skin greenish slate

Cere: greenish gray, horn blue, gray

Bill: base light gray, tip dark gray to black

Tarsi and toes: dull light yellow, banana yellow

Bare parts color data from Ridgway and Friedmann (1950), Wetmore (1965), and Robbins et al. (1985).

Measurements

Total length: 43-49.5 cm (Ridgely and Greenfield 2001b), 46-56 cm (Hilty 2003), 48.5-56 cm (Howell and Webb 1995)

Linear measurements; note that females are larger than males:

ghiesbreghti (Blake 1977)

male, wing length (chord): mean 353.5 mm (range 336-366 mm; n = 6)

male, tail length: mean 225.3 mm (range 221-235 mm; n = 6)

male, culmen length (from cere): mean 25.7 mm (range 24-27 mm; n = 6)

male, tarsus length: mean 82.7 mm (range 80-85 mm; n = 6)

female, wing length (chord): mean 375 mm (range 362-388 mm; n = 5)

female, tail length: mean 226.8 mm (range 222-234 mm; n = 5)

female, bill length (culmen from cere): mean 27.5 mm (range 26.5-29 mm; n = 5)

female, tarsus length: mean 84.6 mm (range 84-87 mm; n = 5)

costaricensis (Wetmore 1965)

male, wing length: mean 346 mm (range 336-358 mm; n = 11)

male, tail length: mean 215 mm (range 209-226 mm; n = 11)

male, culmen length (from cere): mean 26.6 mm (range 25.1-29.0 mm; n = 11)

male, tarsus length: mean 85.8 mm (range 82.0-85.8 mm; n = 11)

female, wing length: mean 367 mm (range 350-377 mm; n = 3)

female, tail length: mean 221 mm (range 215-231 mm; n = 3)

female, bill length (culmen from cere): mean 28.1 mm (range 27.5-28.9 mm; n = 3)

female, tarsus length: mean 85.4 mm (range 83.8-87.5 mm; n = 3)

williaminae (Blake 1977)

male, wing length (flat): mean 342.5 mm (range 323-357 mm; n = 3)

male, tail length: mean 196.6 mm (range 189-201 mm; n = 3)

male, culmen length (from cere): mean 25.6 mm (range 25-27 mm; n = 3)

female, wing length (flat): mean 352.1 mm (range 342-364 mm; n = 6)

female, tail length: mean 209 mm (range 202-217 mm; n = 6)

female, bill length (culmen from cere): mean 27.5 mm (range 27-29 mm; n = 6)

albicollis (Blake 1977)

male, wing length (flat): mean 354.2 mm (range 348-368 mm; n = 7)

male, tail length: mean 193.7 mm (range 176-200 mm; n = 7)

male, culmen length (from cere): mean 26.7 mm (range 25-28 mm; n = 7)

female, wing length (flat): mean 374.5 mm (range 370-379 mm; n = 5)

female, tail length: mean 204.8 mm (range 198-214 mm; n = 5)

female, bill length (culmen from cere): mean 28.8 mm (range 27-30 mm; n = 5)

Mass: costaricensis, female, 650 g (n = 1; Robbins et al. 1985); albicollis, male 605-653 g (n = 2; Haverschmidt and Mees 1994), female 780-908 g (n = 4; Haverschmidt and Mees 1994)

Recommended Citation

Magnier, B. and T. S. Schulenberg (2013). White Hawk (Pseudastur albicollis), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.whihaw1.01