72 Cook et al.: Albino Cape Cormorant

Albinism has been recorded in many vertebrate taxa (Halls 2004). It is a genetic anomaly in which an autosomal recessive gene causes an absence of the enzyme tyrosinase, resulting in a total lack of melanin pigment in the skin, scales, hairs, feathers and eyes (van Grouw 2006). The skin and eye colour of albinos is pink because the blood can be seen through the transparent, unpigmented tissues. In birds, it is the most frequently reported colour aberration, although it is the least frequent in occurrence. This is because it is commonly mistaken for the most frequently inheritable aberration in birds, leucism, which is a partial or total lack of melanin in the plumage (sometimes also in the skin)—but not in the eye—due to an inherited disorder of the deposition of these pigments (van Grouw 2006). There are at least 10 other types of inheritable colour aberrations in birds. Albinistic birds are almost never observed, not only because albinism is rare, but also because albinos have low survival rates (van Grou