The greater white-fronted geese (Anser albifrons) will shortly be leaving our area if they are to arrive in their Arctic breeding grounds by the end of April or early May. This winter, and last winter, amid the large flocks of white-fronted geese was one leucistic individual.
Leucistic birds are those with a genetic mutation that prevents pigments, especially melanin, from properly depositing in the feathers. Leucistic birds can a) have white patches where none are supposed to appear, b) have overall white plumage with little or no color, or, as with the goose I often observed, c) be overall paler in color.
Leucistic birds are not albinos. Albinism is a genetic mutation where there is no pigmentation at all. Albino birds have no color in their feathers at all and their eyes, feet, legs and bills are pink or red. In leucisim there is some pigmentation.
Leucisim confers some disadvantages on birds. The lighter coloration, white color or large white patches can rob the bird of its natural camouflage exposing it to predators. In many species courtship is dependent on the plumage color and display. Leucistic individuals may have more difficulty attracting healthy, strong mates. Melanin pigments are important components in the structure of feathers. Feathers without melanin are weaker and thus could readily break and in the extreme affect the bird’s ability to fly. Finally the white color reflects solar radiation, which could decrease heating in northern climes. Since the pictured leucistic goose is only paler in color and has been here (I naively assume it is the same bird) for two winters, these negative factors do not appear to be severely impacting it.
This leucistic greater white-fronted goose was photographed in Ash Creek Wildlife Area (Modoc County CA). I wonder if it will return next winter?