when the penguin is panting to reduce its body temperature.
Body temperature can be estimated by counting
the number of pants per minute (Boersma 1975).
After the molt, when the penguins are not tied to a site,
they spend more time in the water, and the skin around
the bill and eyes is covered in white or black feathers
(Boersma 1977) (fig. 4b). Before the molt, penguins stop
oiling their feathers, so feathers become brown; after the
molt, feathers are gray-black (Boersma, per. obs.). Unlike
their congeners, Galápagos penguins always lack a white
tail spot (Boersma, unpubl. data).
Immature. The juvenile Galápagos lacks the white feathers
on both sides of the head that outline the cheeks and the
dark feather band around the breast to the legs (fig. 5).
Like the adult, the juvenile has individually distinct dark
feather spots on the breast. The back and head are dark,
and the breast is white. The chin and lower throat are
gray, and the face can be white to gray. Fledglings have
more blue-gray plumage that becomes grayer as they age
and eventually turns brown before the molt. They lose
the feathers around the bill, and by the time they molt,