Pigments in Bird Feathers: What Gives Plumage Its Colors

Bird plumage gets its colors from two sources. The first is pigments, which are colored molecules deposited inside the feather as it grows. The second is feather structure, the microscopic arrangement of keratin and air that bends and scatters light. The two most important bird feather pigments are melanins and carotenoids. Melanins produce blacks, grays, browns, rusts and buffs, and the bird makes them itself. Carotenoids produce most bright yellows, oranges and many reds, and they come from the bird's food. Most blues, and the shimmering iridescence on a grackle's head, come from structure rather than pigment.

Knowing this changes how you watch birds. A meadowlark's yellow breast, a longspur's chestnut collar and a bluebird's sky-blue back each tell a different story about diet, molt, light and season. The sections below explain each kind of color, what you can notice in the field and how to record it.

What are bird feather pigments?

Bird feather pigments are colored compounds laid into a feather while it is still growing inside its follicle, the small pocket in the skin where the feather forms. This process is called pigment deposition. Once a feather finishes growing, it is dead keratin, much like a fingernail. Its pigment cannot be added or removed. After that point the color changes only through wear, fading in sunlight or staining from the environment, until the feather is replaced during molt.

This has a practical consequence. The colors you see on a bird today were mostly set weeks or months ago, when those feathers grew. A bird's plumage is partly a record of its past condition and season.

The main groups of bird plumage pigments

• Melanins are the most widespread bird plumage pigments. Nearly all birds have them.
• Carotenoids come from plants and algae, and birds obtain them through their diet.
• Porphyrins are less familiar pigments found in some groups, including owls. They can give feathers soft brown or pinkish tones. Many porphyrins glow reddish under ultraviolet light and break down with sun exposure, so they are most noticeable in fresh feathers.
• Other specialized pigments occur in particular bird families, such as the psittacofulvins that color many parrots. You will rarely meet these on a prairie walk.

How does melanin color bird feathers?

Melanin is a pigment that birds produce in specialized cells called melanocytes. These cells pass melanin granules into the growing feather. Melanin comes in two main forms:

• Eumelanin produces black, dark gray and dark brown.
• Pheomelanin produces reddish-brown, rust, chestnut and buff.

By varying the amount and mix of these two forms, birds produce the endless browns, streaks and bars that make prairie birds so beautifully camouflaged. The streaked backs of sparrows, the earthy tones of a Horned Lark and the barring on a female Northern Harrier are melanin-based patterns.

Why melanin matters beyond color

Melanin makes feather keratin tougher and more resistant to wear. This is a widely accepted explanation for why many pale birds still have black wingtips. American White Pelicans and Snow Geese, both familiar over prairie wetlands, are white birds with black outer flight feathers. The darker primaries are thought to hold up better against abrasion.

Field tip: When you see a white or pale bird in flight, check the wingtips. Dark tips on an otherwise pale bird are a good example of melanin doing structural work as well as decorative work.

How do carotenoids create yellow, orange and red plumage?

Carotenoids are yellow, orange and red pigments made by plants, algae and some microbes. Birds cannot make carotenoids themselves. They must eat them, either directly in seeds, fruits and plant material or indirectly through insects that ate plants. After eating them, many birds can chemically modify carotenoids, for example converting yellow forms into red ones before depositing them in feathers.

On the prairie, carotenoids are behind many of the brightest colors you will notice:

• The yellow breast of a Western or Eastern Meadowlark
• The golden head of a male Yellow-headed Blackbird
• The yellow of a breeding male American Goldfinch
• The yellow wash on a Dickcissel's chest

Why carotenoid color can vary between individuals

Because carotenoids come from food, carotenoid-based color can reflect what a bird ate and how healthy it was while its feathers were growing. The male House Finch is a well-studied example. Males range from yellow to orange to deep red, and diet during molt plays a large role in that variation.

Diet can also produce surprising colors. Some Cedar Waxwings show orange rather than yellow tail tips. This has been linked to a red carotenoid in the berries of certain non-native honeysuckles eaten while tail feathers were growing. It is a clear example of a bird's surroundings shaping its plumage.

Field tip: If you notice an unusually pale or unusually orange individual among yellow birds, note it. Variation in carotenoid color is normal and worth recording calmly. It is not automatically a sign of illness or a rare plumage.

What is structural coloration, and how is it different from pigment?

Structural coloration is color produced by the physical structure of a feather rather than by pigment. Tiny arrangements of keratin, air pockets and melanin granules scatter or reflect particular wavelengths of light. Two kinds are especially easy to see:

• Non-iridescent blue looks the same from most angles. Mountain Bluebirds, Eastern Bluebirds, Indigo Buntings and Blue Grosbeaks owe their blue to feather structure, not to a blue pigment.
• Iridescence shifts in color as the viewing angle changes. The purple and bronze gloss of a Common Grackle, the green-purple sheen of a European Starling and the blue-green back of a Tree Swallow are structural.

White plumage is usually also a structural effect. When a feather lacks pigment, its keratin and air scatter all wavelengths of light roughly equally, and we see white.

When pigment and structure work together

Many colors combine both sources. Dark melanin often sits beneath structural layers and makes blues and iridescence look richer by absorbing stray light. Many green feathers, especially in parrots, combine a structural blue effect with a yellow pigment. Understanding this helps explain why a bird's color can look so different in sun and shade.

How can you tell pigment from structural color in the field?

You can often tell pigment color from structural color by watching how the color behaves as light and angle change. Pigment colors stay fairly steady. Structural colors can shift, darken or even appear black in poor light.

Simple steps for reading color on your next outing

1. Note the light first. Write down whether the bird was in full sun, shade, overcast light or backlit. Backlit birds often look darker and less colorful than they are.
2. Watch for shifts. If the bird turns and the color changes from bronze to purple, or from bright blue to dull gray, you are likely seeing structural color.
3. Look at the pattern, not only the hue. Streaks, bars and scalloping are usually melanin patterns. Solid bright yellow or red patches are often carotenoids.
4. Compare similar birds. When several birds of the same species are together, notice differences in brightness or tone. These may reflect age, sex, diet or season.
5. Record what you saw, not what you expected. If a goldfinch looks olive or a bluebird looks gray, write that down along with the light conditions.

How do seasons change plumage color?

Seasonal color changes on the prairie come from two main processes: molt and feather wear. Because pigment is fixed once a feather has grown, a bird changes its look either by growing new feathers or by wearing away parts of old ones.

Molt: growing new colors

Molt is the regular replacement of feathers. Many birds undergo more than one molt a year. The male American Goldfinch is a familiar example. In late winter and spring he molts into bright carotenoid-yellow body feathers, and after breeding he molts into a duller, olive-brown winter plumage. If you watch goldfinches at a prairie edge in early spring, you may see patchy yellow-and-brown males partway through this change.

Wear: revealing hidden colors

Some birds change color without molting at all. Their fresh fall feathers have pale or buffy tips that slowly wear away over winter, revealing darker or bolder colors underneath. Snow Buntings, European Starlings and male Bobolinks all show breeding colors that become more striking as feather tips wear down. A starling that looks heavily spotted in fall can look glossy and nearly unspotted by spring with no new feathers involved.

Fading and staining

Sunlight gradually fades many pigments, and some, like porphyrins, fade especially quickly. By late summer, many birds look paler and more worn than they did in spring. Birds can also be stained by their surroundings. Sandhill Cranes sometimes look rusty because they preen iron-rich mud into their gray feathers. That rusty color sits on the surface and is not a pigment inside the feather.

Field tip: Keep a simple seasonal page in your field notebook for a few common species. Note the date and how bright, worn or patchy each bird looks. Over a year, you will see molt and wear unfold in a way field guides can only summarize.

How do pigments relate to unusual plumage?

Many unusual-looking birds are the result of changes in how pigments are produced or deposited. A short overview helps you describe what you see accurately:

• Leucism is a reduction in pigment deposition. It can produce white patches or an overall pale bird, while eye color typically stays normal.
• Albinism is the inability to produce melanin. True albino birds are entirely white or pale where melanin would normally be and have pink or red eyes. Carotenoid colors may still appear.
• Melanism is an excess of melanin, making a bird darker than usual.

Before deciding a bird has an unusual pigment condition, consider simpler explanations first: strong backlighting, worn feathers, mid-molt patchiness, staining or a young bird in a plumage you have not seen before. Careful notes and a photograph, if you have one, will help you or others review the sighting later.

How to prepare for observing plumage color

Observing plumage color well depends more on patience and light than on special equipment. A little preparation helps:

1. Plan for good light. Early morning and late afternoon light is soft and warm and often shows color well. Try to keep the sun behind you so birds are lit from the front.
2. Bring binoculars you know well. Practice focusing quickly so you can catch a bird as it turns and shows structural color shifting.
3. Carry a small notebook and pencil. Pencil works in cold or damp prairie weather. Include space for date, time, light conditions, location and plumage notes.
4. Dress for the season. Prairie wind and open sun can be tiring. Comfortable layers, a hat and water let you stay still and watch longer.
5. Give yourself time. Sitting quietly near a wetland edge or fence line for twenty minutes often shows you more color variation than walking quickly past many birds.

Observing respectfully

Watching color closely should never come at a bird's expense. Keep a comfortable distance, especially around nests and during the breeding season, and step back if a bird changes its behavior because of you. Stay on established trails where they exist so you do not trample nesting grasses.

You may find molted feathers on the ground, and they are wonderful for seeing pigment and pattern up close. Look, sketch or photograph them, then leave them where they lie. In the United States and Canada, migratory bird protection laws generally prohibit keeping feathers of most native wild species without a permit.

Bringing it into your next outing

The next time you watch prairie birds, try to sort each color you see into a simple question: is this melanin, carotenoid or structure? Notice the steady browns and streaks of melanin, the food-derived yellows of a meadowlark and the blue of a bluebird that dims as it moves into shade. Write down the light, the date and anything that surprises you. Over the seasons, your notes will show how bird feather pigments and feather structure combine with diet, molt and weather to create the colors of the open grassland.