NEDERLAND — We’ve all seen birds do it at some point in our lives. We’ve even adopted the term for humans, applying it to the actions of individuals who tend to spend a lot of time in front of a mirror.

While long thought to be a process of simply improving one’s looks, the art and science of preening is more complex and far more important than appearance. 

The reason for the process was long misinterpreted only as a way of improving looks. Birds meticulously work through their feathers, pulling them out individually with their bills, rearranging them, ruffling them, doing more rearranging, more ruffling—rinse, wash, repeat. Some spend hours doing it, and in the end, sometimes do look better for the work. 

Outside of wings, feathers are one of the main anatomical features that separate birds from other animals. The chemical makeup is much the same as hair, but the structure is immensely more complex. Going far beyond simply providing warmth, feathers are necessary to help give better loft for flight and are also vital to the animal’s aerodynamics.

Specific feathers vary in shape and use, but the structure is relatively the same. Using a tree as an analogy, each feather has a hollow “trunk” known as a rachis. From this trunk grow “branches” called barbs.  

Feathers necessary for flight, like those found on wings and tails, have even smaller structures called barbules. The barbules are like hooks, and keep the outer feathers locked together to create the uniform surface necessary for loft and aerodynamics. They also protect the down feathers from the elements.

As they can become misaligned in various ways, preening puts both barbs and barbules back into alignment, “re-locking” them like Velcro. 

Down feathers purposely grow non-uniformly and without barbules.  This lack of uniformity and complex structure creates air pockets that help to keep the bird warm.  Unfortunately, the air pockets also provide places for parasites like mites and lice to live. Baths, whether with dirt or water, help to release the pests, and preening pulls them from the feathers to become part of the bird’s diet.

Another vital part of preening for many birds is to cover the feathers with an oil known, understandably, as preen oil. It is secreted from the uropygial gland, located towards the base of the spine at the tail.  The birds who have this gland (most but not all do) can be seen “nibbling” at this gland, then using their bills to apply the oil to individual feathers.

The main purpose of the oil is to provide waterproofing for the feathers, helping to insulate the birds. It also doubles as an aid to basic aerodynamics, as it further helps to keep the barbs and barbules in place.  

Swimming birds understandably have the largest uropygial glands, as they require far more oil. Insulation is understandably of great importance, especially with birds like our American Dippers, who swim for their prey all year long in icy waters.  A second purpose is—similarly to their aero cousins—hydrodynamics and streamlining for their swimming.

Looking closely at any bird will show some incredibly complex layering of all feathers, each with their own importance. So it is understandable why birds spend so much time preening to take care of their plumage.  

All of that said, birds in general do tend to exhibit some of the highest standards when it comes to beauty in the animal kingdom. Ignoring the science behind the preen, our misunderstanding of the need to retain that beauty does seem to fit the bill (pun intended).

Sources for this article included information from ornithology.com/the-preen-gland and audubon.org/news/the-science-feathers.

For additional information about James DeWalt Photography, check out jamesdewaltphotography.com.