The Galapagos Penguin is a member of the genus Spheniscus, all of which are medium sized penguins with blackish upperparts, a white white outlining the side of the face, a white belly that is bordered with a black crescent across the breast and flanks, and a stout bill. The Galapagos Penguin is the both the smallest and northernmost Spheniscus. Although it is endemic to the Galapagos Islands of Ecuador, it is still similar in morphology to its closest relatives that are native to South America; see Similar Species.
The Humboldt Penguin (Spheniscus humboldti) is one of the closest relatives to the Galapagos Penguin and is very similar in appearance. The Galapagos Penguin has much less bare pink skin at the base of the bill, but has more extensive pink on the mandible. Galapagos Penguin also has a much narrower, less prominent white stripe connecting on the side of the face. In addition, the two species are allopatric. Galapagos Penguin is endemic to the Galapagos islands, whereas the Humboldt Penguin inhabits the shores of central Peru down to Chile (Luna-Jorquera et. al. 2000).
Another similar species in South America is the Magellanic Penguin (Spheniscus magellanicus), another allopatric species of southern South America and the Falkland Islands. The Magellanic Penguin has a very broad white line on the side of the face, the bill is entirely black, and it has two black bands across the breast.
Adult: Small in comparison to other Spheniscus penguins. Head black with white stripe from eyebrow, around black auriculars and chin, connecting at the throat. Upperparts entirely black. White breast and belly with a black stripe across chest that runs down the sides to the flanks. Wings entirely black wings (Swash and Still 2000).
Males are typically larger in size and have bolder markings and more pink around the base of the bill and around the eyes than females. Males white chins are broader and more obvious with less mottling than those of females. The pectoral bands, and facial markings of males are more distinct than those of the females (Boersma 1977).
Juvenile: Dark brown. Gray or white checks. Lacks any bars.
They molt as a prelude to breeding (Boersma 1977).
Molting occurs once the penguins have enough fat stores to sustain the bird on shore for 10 to 15 days, during which time they do not reenter the water. Because both reproduction and molting are very energy expensive, in years when food is scarce, it is unlikely that birds will be able to do both and survive. While reproduction is important, it is more vital that a penguin (or any bird) has a healthy coat of feathers. Therefore, the Galapagos Penguin shows an ability to molt completely before beginning breeding (Boersma 1978).
Iris: brown "in older adults"
Bill: maxilla and tip of mandible black; base of mandible black, with yellowish or whitish area exending to near tip
Tarsi and toes: black with white mottling; soles black
Bare parts color data from Williams (1995).
Height: 48-53 cm (Restall et. al. 2006).
Linear measurements (from Boersma 1976):
Bill length, male: mean 58.2 mm ± 0.3 (n = 93)
Bill length, female: mean 53.9 mm ± 0.2 (n = 83)
Bill width, male: mean 20.0 mm ± 0.4 (n = 93)
Bill width, female: mean 16.6 mm ± 0.1 (n = 84)
Flipper length, male: mean 118.7 mm ±0.8 (n = 79)
Flipper length, female: mean 114.1 mm ± 0.7 (n = 71)
Mass: male, mean 2118.8 g ± 37.9 (n = 33)
female, mean 1877.9 g ± 29.8 (n = 34)