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The Case of the Cinnamon Wren

I photographed these two "cinnamon" birds within two weeks of each other. What are the odds of seeing two songbirds with similar pigmentation issues? I should have bought a raffle ticket.

House Wren with pigmentation issues
Why does this Cinnamon House Wren look so ratty? Molt. (Or moult for my UK ringers.)

This House Wren was captured during MAPS bird banding efforts in Wyoming. It was a hatch-year bird, showing a plumage aberration. We promptly named it "The Cinnamon Wren."


Before we examine these two examples of unusual plumage coloration, let's establish a basic understanding of how feathers get their colors. Please, make sure to subscribe to the blog, here!



Pigment vs Structure in Birds

The colors in the feathers of a bird are formed in two different ways. For many species, feather color comes from pigments, and for others, feather color is a result of light refraction caused by the structure of the feather. In some cases, feather colors are the result of a combination of pigment and structural colors. Green-colored feathers in some parrots are the result of yellow pigments overlying the blue-reflecting characteristic of the feathers.


Today's unusually colored birds are a result of pigmentation issues, so we will not address structural coloration in this post.



Pigments in Bird Feathers

There are three "main" different classes of pigments found in birds.


  1. Carotenoids

  2. Melanins

  3. Porphyrins


Carotenoids

Carotenoids are produced by plants and birds acquire them by eating something (like an insect) that has eaten the plant, or by eating a product of the plant itself. Carotenoids are responsible for reds, yellows, and oranges. A combination of pigments can create other colors, ie carotenoids + melanins = greens of the tanagers.


Melanins

Melanins occur in the skin and feathers of birds, unlike the carotenoids. They can produce colors ranging from black to reddish-brown to pale yellows. Additionally, melanins provide structure to feathers. There are many complex factors that are involved in the production of melanins but diet and hormones are both highly involved.


Porphyrins

Porphyrins are not as frequently found in the bird world. They are produced by modifying amino acids and create pinks, browns, reds, and greens. Anyone who has experienced an owl being banded might know these pigments for their ability to fluoresce bright pink or red under ultraviolet light.