Various types of unusual penguins call Antarctica and the sub-Antarctic home, including penguins with different plumage colourations and hybrid penguins (offspring of cross species mating). Both hybrid penguins and penguins with non-standard plumage are relatively rare.
Unusual plumage colourations (or colour aberrations) can be caused by a variety of factors including injury, diet and disease. But many are due to mutations (alterations in genetic material). Some of those can be identified by just looking at a bird. However, the nature of others can really only be determined properly through genetic analyses.
Generally speaking, plumage colouration is important in birds as a visual signal that identifies a bird’s species, sex, age and even health. Penguins, like all seabirds, lack the wide range of colours found, for example, in parrots. But plumage colour is still important to identify young from mature birds, for example. Before penguins moult their plumage looks dull and often nearly brown; all feathers need to be replaced every year because after having been exposed to sun, sea salt and other environmental factors they are pretty much worn out. Once the penguins have undergone their annual moult, their plumage is soft and shiny, and the brand new feathers are again deep grey or black.
Only some penguin species sport yellow feathers on their heads and chests but all have a basically black and white body. These yellow pigments are unique to penguins. The dark colouration of the feathers is due to two pigments called phaeomelanin and eumelanin (collectively known as melanins). At times, the plumage colouration of individuals is very different from the norm. It is often difficult to determine the type of mutation that has taken place just by looking at a penguin. But some conditions are relatively straight forward.
The extremes in colour aberrations range from ‘melanistic’ (a penguin whose normally white parts are black) to ‘albinistic’ (a penguin that lacks both melanins and is totally white). An albinistic penguin, or an albino, also lacks any pigments in its beak, skin and eyes. Due to the lack of pigment, these parts are pink. Sometimes people mistakenly talk about ‘partial albinos’ when they see penguins that have more white feathers than normal. But a bird cannot be a partial albino because the mutation that causes albinism means that no cell in a bird’s body can produce the pigments. Calling a bird a partial albino is like calling a woman partially pregnant. Albinism is a serious condition for penguins; they usually do not live very long because they tend to become blind and can no longer fend for themselves.
However, there are completely white penguins whose beaks and eyes are pigmented and look normal. These birds are ‘leucistic’ or leucinos. ‘Leucos’ is the Greek word for white. The mutation causing leucism enables the production of the pigments in the epidermis, but the mechanism to deposit the melanins into the feathers is faulty. Also, not every pigment-producing cell is necessarily affected. That means in contrast to albinism, penguins can be partially leucistic. The degree of leucism can range from just a few feathers to the entire plumage. Hence, leucism is possibly the mutation that produces the greatest variety of colour aberrations. Thus, it is important to realise that not every bird with only white feathers is an albino.
A relatively common aberration is simply known as ‘brown’; here the appearance of the eumelanin is altered so that the penguins appear brown and white rather than black and white. The brown feathers are very sensitive to sunlight and can fade over time when exposed to sunlight. Brown birds can have somewhat paler beaks and feet as well.
Mutations that can affect both melanins are called ‘dilution’. This mutation has many gradations as the feather colour depends on the degree of melanin reduction. The pigments themselves are not changed but the amounts of pigments deposited are reduced. Among penguins, the black feathers are grey and the affected penguin has a washed out appearance.
Even more extreme than the dilute mutation is ‘Ino’. When this mutation occurs the black feathers are very pale brown and can look nearly white, especially in late summer. Over time, the plumage gets bleached by the sun.