Photo Stefan Rust
Abnormally white feathers in bird plumage is called leucism, a situation in which some feathers have scant deposits of pigment. This is caused by defective genes that restrict the body's melanin from entering certain feathers or feather groups. Some people confuse leucistic birds with albino birds or partial albino birds. Albino birds have a genetic mutation which generally results in a lack of melanin in their bodies and plumage. Eyes, skin, beak, legs and feet typically have no color unless carotenoids, organic pigments that come from plants in the birds' diets, enter some feathers, giving albino birds slight coloration. But albinism in birds is extremely rare, whereas leucism may not be quite as rare, but is certainly highly unusual. Leucistic birds are not albinos because they have normally colored eyes, beaks, legs and feet.
Environmental hazards do play a role in leucism and albinism. Birds with abnormally white feathers, whether due to albinism or leucism, have little chance of survival because they are highly conspicuous to predators. They also don't easily attract a mate due to lack of their specific species color.
Photo Elke Hoeltzcke
Double-banded coursers (Rhinoptilus africanus) breed in monogamous pairs. After the mating dance of the male, the female then lays one egg, which the parents take hour-long shifts incubating.