Leucistic House Finch

By josh • Nature, Wildlife • 4 Dec 2012

Apparently it’s deformities month at Casa Phillips.  A leucistic female house finch has joined the cardinal with a bill problem in my yard.

Leucistic House Finch

Leucistic House Finch
Canon 400mm f/5.6L at f/5.6, 1/80s, ISO 400

Leucism is caused by a recessive gene that effects the distribution of all pigments (including melanin) to skin and feathers.  Project Feeder Watch’s excellent post explains why this bird is leucistic rather than albinistic:

…since birds with white patches do have melanin in the body, they cannot be albinistic.  Therefore the white patches are caused by a defect preventing normal deposition of the melanin. And since leucism is a deposition problem, it makes sense that birds with white patches would be leucistic. Consequently leucism comes in two main varieties — paleness, an equal reduction of melanin in all feathers; and pied, an absence of melanin in some feathers creating white patches.

This piebald finch is constantly in the presence of a male, so I don’t think she’s had trouble finding a mate and perhaps she’ll pass along her odd trait.  I do wonder if her notable brilliant white forehead will make a nice target for our resident Cooper’s Hawk though.  Her pigment-free patch is pretty small relative to some of the images in the link above- it’s entirely restricted to her crown.

Leucistic House Finch

Leucistic House Finch
Canon 400mm f/5.6L at f/5.6, 1/100s, ISO 400

The total lack of pigment also creates a difficult exposure problem.  Even in our dim late fall light, I was unable to find an exposure that properly lit both the pigment-free feathers on her crown and the darker portions of her drab plumage.

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