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Birds of mud

This Sunday morning I went for a walk with my friend Irene in the area of ​​Santa Eulalia la Mayor, in the Hoya region of Huesca (Spain).

Irene - who is an environmentalist, a great lover of nature and a connoisseur of birds - has seen a Bearded Vulture with her binoculars. She told me that it was difficult to find them with the naked eye, since they are animals that tend to hide quite a bit.

We were talking about bird feathers, how they vary depending on the species.

Feathers are incredibly versatile, promoting flight, thermally insulating, and also serving as camouflage or warning. Some birds have drawings captured in their feathers that are witnesses of the wind waves that they have flowed through for thousands of years.

When we looked at the Bearded Vulture (Gypaetus barbatus), she told me that its plumage is white. I kept thinking... Wasn't it red? And she answered me smiling: not exactly. Their plumage is white, but they paint it with red ferruginous mud.


This very particular behavior has been called cosmetic coloration. Cosmetic coloration in birds has several origins: that produced by the bird itself (uropygial and skin secretions, feather dust) or obtained from the environment (earth pigments, iron oxide).

The reason why this bird performs this action is discussed. One of the theories contemplated in the latest research carried out (2023) is that painting is an expensive task, as it requires knowing very specific geographical areas that are not easily accessible. Thus, Bearded Vultures would want to demonstrate their orientation and gathering skills to their future mating partners.

Another of the most discussed theories is cosmetic coloring in specimens with poorer quality plumage, which would use the color as a 'makeup', an evolutionary strategy to hide their disadvantage when it comes to reproduction.

Bearded Vulture bathing in a ferruginous water.

An interesting fact is that females, which are the dominant sex in this species, have greater pigmentation both in their natural habitat and when raised in captivity.

Cosmetic coloration has been seen in 29 species of birds, belonging to 13 different families.

In this link you can see how a Bearded Vulture bathes in a stream of ferruginous water in the Ordesa and Monteperdido Natural Park.

Humans have been practicing body painting since the beginning of time, and there are examples of it all over the planet. The colors used have been mainly ferruginous clays and some plants with very notable dyeing capacities.

Body painting in humans has probably been inspired by these birds which they shared habitat with. We have always imitated animal behaviors ranging from cosmetics to housing and engineering.

Today there are various groups of people who use body paint based on ferruginous mud to denote a certain status within the community. This red mud also protects from ultraviolet rays as well as bacteria.

Himba Tribe (Namibia)

Last year I carried out a research on the different mineral pigments of the province of Huesca, the place where I live.

I observed quite clearly that the best pigments in terms of intensity and light resistance were those richest in Iron Oxide (orange, red and garnet tones). In the following image you can see the results obtained on cotton fabric and different dyeing procedures.

We are preparing different courses in which you can discover more about the fascinating world of NATURAL COLORS, always from a curious and respectful perspective towards the environment.


Margalida, Antoni, Ivan Almirall, and Juan J. Negro. 2023. “New Insights into the Cosmetic Behavior of Bearded Vultures: Ferruginous Springs Are Shared Sequentially,” Animals 13, no. 15: 2409.

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