Lipochromes Create Red Feathers

bright blue, green, yellow and red feathers of a scarlet macaw fill the frame

Biological Strategy

Scarlet macaw

AskNature Team

Image: Brian Gratwicke / Flickr / CC BY - Creative Commons Attribution alone

Modify Light/Color

Color in living systems comes from pigments and the interaction of light with surfaces. Color serves many purposes for living systems, such as attracting prey or mates, providing warnings, or protecting through camouflage. To create the effects needed for each purpose, living systems must control the expression or visibility of pigments and the interactions (such as reflectance and refraction) of light. To do so, they have strategies that modify color or light to increase or decrease the color’s position, intensity, opacity, and more. Male hummingbirds, for example, have brightly colored feather patches on their throats; the coloring comes from pigments, structures that refract light, or a combination of the two. When a male hummingbird hovers near a potential mate, it modifies the angle of these feathers to create a bright, colorful display. However, when it needs to mute the colors to reduce conspicuousness, such as to avoid a predator, it modifies the angle again.

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Send Light Signals in the Visible Spectrum

The visible spectrum is the portion of the electromagnetic spectrum that the human eye can detect. Visible light can be thought of in two ways–light as illumination (such as that used by fireflies) and colors that result from light being absorbed or reflected. Living systems use light for a variety of purposes. Sometimes, they use it to make themselves highly visible (like a peacock showing off his brilliant feathers to a potential mate). Other times, they use it to become virtually invisible (like an owl hiding in plain sight when it rests during the day). When a living system sends a light signal, it must create that light or color in an energy- and material-efficient way. Living systems create and enhance color using such strategies as non-toxic pigments, structures that bend and absorb different wavelengths, and chemical processes that create bioluminescence.

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Birds

Class Aves (“bird”): Eagles, hawks, sparrows, parrots

Birds are evolutionary engineering marvels. They are descended from dinosaurs, but are far from our idea of heavy, scaly reptiles. Of the specific adaptions that set them apart, most notable is flight—although some mammals can fly, birds take the prize for abundance in the skies. Many birds have hollow, lightweight skeletons and specially-designed wings to help them stay aloft. They also have feathers made of keratin that help them stay warm, attract mates, and improve navigation and aerodynamics in flight. In contrast to their dinosaur ancestors, they lack true teeth and have replaced them with specialized beaks and bills.

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The feathers of scarlet macaws gain their red coloration via five lipochromes produced only in parrots.

Image: en:User:Cburnett / Wikimedia Commons /

'''en:''' A Scarlet Macaw at the <a href=http://commons.wikimedia.org/w/index.php?title=Henry_Doorly_Zoo&action=edit&redlink=1 class=new title=Henry Doorly Zoo (page does not exist)>Henry Doorly Zoo</a> in <a href=http://commons.wikimedia.org/wiki/Omaha,_Nebraska title=Omaha, Nebraska>Omaha, Nebraska</a>.

Image: Adrian Pingstone / Wikimedia Commons /

OLYMPUS DIGITAL CAMERA

Image: ??????? | / Wikimedia Commons /

Image: Petra Karstedt / Wikimedia Commons /

Image: Donar Reiskoffer / Wikimedia Commons /

Ara macao

Image: Wikimedia Commons /

Image: VC-s / Wikimedia Commons /

Image: Christoph Diewald /

Close up of feathers of a scarlet macaw.

“In this first examination of the variety of colourful s present in parrot feathers, we studied 44 parrot species from 27 genera and found that they all use the same set of five lipochromes to colour their feathers red…Red parrot feathers also differ in colour intensity, from the light-pink hue of several cockatoos to the deep red of red lories (Eos bornea)…The only reports of these pigments in nature are from parrot feathers…There are several other lines of evidence that point to a non-dietary origin of these pigments, including (i) the absence of these pigments from diet samples of certain captive parrots (K.J.M., personal observation) and (ii) the ability of parrots to maintain striking plumage colouration in captivity despite tremendous variation in diet (which is not the case for diet-derived colouration; reviewed in Stradi et al. 2001). Stradi et al. (2001) supposed that parrots derive these acyclic polyenal lipochromes either by the addition of acetate units to acetyl CoA or by fatty-acid desaturation. What remains unclear is why parrots are the only group of organisms capable of manufacturing/harbouring these colourants.” (McGraw and Nogare 2005:41-42)