It is common to say that something is as light as a feather in order to mean that something doesn’t weigh much at all. A group of researchers, however, has found that while all feathers are pretty light, some of them are quite a bit heavier than others, and it may be because of their color.

Bird feathers come in all different colors ranging from black to white, and everything in between. The specific colors that a particular species of bird evolved can have many factors. This can include things like camouflage, visual communication, attracting a mate, and more. According to a new study published in the journal Biology Letters, another reason for the color of the bird may be weight.

When it comes to flying, one of the most important factors is how much something weighs. The heavier it is, the more energy is required in order to get it off the ground and keep it in the air. That applies to birds as much as it does to planes.

So, the researchers wanted to know if there was a difference in how much a feather of one color weighed compared to that of another color. They studied 109 specimens of bird across 19 different species.

The team looked at many different things in the study, including looking at the melanin in the feathers. Melanin is a compound that is found in the feather follicle of birds, and as the feather grows out, the melanin goes into the keratin structures. Melanin has a fairly high molecular mass, which means that it becomes a not-insignificant portion of the overall weight of the feather itself.

There are two form of melanin, which are pheomelanin, which is found in light brown and orange hues, and eumelanin, which is found in black, grey, and darker brown feathers.

Once the researchers had the feathers they needed, they exposed them to sodium hydroxide (NaOH) in order to disrupt the keratin matrix. From there, the melanin from the feathers was separated out using centrifugation. Finally, it was purified using hydrochloric acid (HCI) and distilled water before being dried out.

The team then weighed the extracted melanin and compared it to the weight of the feathers before the melanin was removed.

They found that the melanin accounted for about 25% of the total dry mass of the feathers, on average. For a species of raven known for having very dark feathers, that went up to over 60% of the weight.

Of course, feathers are pretty light and generally make up a small overall percentage of the total weight of a bird. So, 25% of the weight of feathers is still going to be very little.

That being said, when it comes to flying, every little bit counts. It is pointed out that migratory birds tend to have lighter colored feathers, which could help them to fly more efficiently over great distances. Also, many birds that live in very cold climates have light feathers, which may allow the birds to grow them in thicker layers, which could help to keep them warm.

More study is needed to determine exactly how much of an effect on a given species of bird this would have, but it appears that the extra weight of darker feathers is at least one factor among many involved when it comes to how evolution progressed in different species of birds.

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