Guanay Cormorant Phalacrocorax bougainvillii

  • Order: Suliformes
  • Family: Phalacrocoracidae
  • Monotypic
  • Authors: Mark A. Baran and Michael G. Harvey
Sections

Appearance

Distinguishing Characteristics

A large, two-toned cormorant, with blackish upperparts and a white breast and belly. There is a small area of bare red skin on the face, surrounding the eye. Immatures are similar in pattern, but are paler (brown) above.

Similar Species

The Guanay Cormorant is broadly sympatric with two smaller species, Neotropic Cormorant (Phalacrocorax brasilianus) and Red-legged Cormorant (Phalacrocorax gaimardi).  Neotropic Cormorant is smaller, and is entirely blackish (adult) or brown (immature), lacking the extensive white underparts of Guanay. Neotropic also has an orange buff gular patch, and lacks red on the face. Red-legged Cormorant has red at the base of the bill, but is gray rather than black, does not have white underparts, and  has a distinctive white patch on the side of the neck.

There is little or no overlap in range between Guanay and Magellan Cormorant (Phalacrocorax magellanicus), but these two species are more similar. Rock Cormorant is smaller than Guanay, has a black breast, the red on the face is more extensive, and, when breeding, has a white patch on the side of the head. Guanay Cormorant overlaps on the coast of Argentina with Imperial Cormorant (Phalacrocorax atriceps), which also is black above and white below; but Imperial has no red on the face, has yellow carbuncles at the base of the bill (a feature lacking in Guanay), and usually the white of the underparts extends onto the sides of the face.

Detailed Description

The following description is based on Blake (1977); see also Murphy (1936):

Adult: Sexes similar. Appears black above at any distance, but head and most of neck glossy blue-black; remaining upperparts greenish black. Chin and upper throat white. Lower neck, breast, and belly white. Undertail coverts dark. When breeding, has small dark nuchal crest, a patch of white plumes above the eye, and a few white plumes on neck.

Juvenile: Resembles adult, but duller and browner above, and lower neck more extensively white.

Molts

No information.

Bare Parts

Data from Murphy (1936):

Iris: Dark brown

Facial skin: A narrow area of bare, olive-green skin surrounding the eye, in turn surrounded by broader area of bare red skin. This red skin is tinged somewhat orange above the eye, and somewhat brownish behind the eye.

Bill: Horn or brownish black; faint pinkish and bluish tones at base of mandible.

Gular sac: Brownish.

Tarsi and toes: Flesh, sometimes pinkish.

Measurements

Total length: 71-76 cm (Blake 1977), 76 cm (Jaramillo 2003)

Linear measurements (Murphy (1936):

Males (n=5):
Wing length: mean 296.4 mm (range 281-303 mm)

Tail length: mean 100 mm (range 96-104 mm)

Tarsus length: mean 68.8 mm (range 66-71 mm)

Bill length (exposed culmen): mean 71.4 mm (range 65-78 mm)

Females (n=4):
Wing length: mean 281 mm (range 270-287 mm)

Tail length: mean 103.3 mm (range 96.6-108.5 mm)

Tarsus length: mean 66.6 mm (range 66-67 mm)

Bill length (exposed culmen): mean 69.1 mm (range 86-99 mm)

Mass: ca. 2 kg (Jordan 1966)

Recommended Citation

Baran, M. A. and M. G. Harvey (2011). Guanay Cormorant (Phalacrocorax bougainvillii), version 1.0. In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/nb.guacor1.01