The waterproofing abilities of birds’ wings is a fascinating topic. In the opening paragraphs, we’ll provide a quick overview of the answer, which is that most, but not all, birds have waterproof feathers that help keep their wings dry while swimming or flying through rain. However, some birds, like chickens, have only partially waterproof plumage. Keep reading for more details!
Waterproof Feathers
The majority of birds have feathers that are waterproofed by secretions from a gland called the uropygial gland, also known as the preen gland. This gland produces an oily substance that birds spread over their feathers when they preen. The oil coats the feathers and causes water to bead up and run off the surface rather than saturating the feather.
The microscopic structure of feathers also contributes to their waterproofing abilities. Feathers have barbs coming off a central shaft. These barbs have even smaller structures called barbules with hook-like structures that zip them together. This creates a tight weave that prevents water from penetrating through the feather.
In addition, feathers contain a fluffy downy underlayer that provides insulation. This down layer gets ruffled up when the bird preens, helping to maintain its water-resistant loft. So in summary, the special oil, tiny barbules, and downy underlayer make most birds’ feathers waterproof.
Waterbirds
Birds that spend most of their time on the water, such as ducks, geese, and swans, have feathers specially adapted for swimming. Their feathers have a more densely packed microstructure and enhanced waterproofing from both the preen oil and an extra layer of waxy microscopic particles on the surface of the feathers.
The feathers of diving birds like loons and cormorants are also equipped with superior waterproofing and structural adaptations like greater feather density and stiff shafts that maintain insulating air pockets even when the bird is underwater. Additionally, some water birds like ducks and geese have fewer blood vessels in their legs and feet, preventing excessive heat loss while paddling in cold water.
Soaring Birds
Soaring birds like eagles, vultures, and albatrosses have long, broad wings suited to catching air currents. Their wings need to be both lightweight for gliding and soaring, yet also sturdy. To achieve this balance, their feathers have stiff shafts but are porous or not perfectly interlocking. This means their wings are not fully waterproof.
However, partial waterproofing is adequate for their purposes, since they take care to limit flying in the rain which would dampen their flight feathers and cause them to lose lift. When rainfall is unavoidable, they are often seen holding their wings in a characteristic dihedral or slight “V” shape to limit feather exposure to the rain.
Chickens and Other Flightless Birds
Birds that do not fly generally have poorer waterproofing than soaring or aquatic birds. The feathers of flightless birds like ostriches, emus, and kiwis lack the complex interlocking barbules of wing feathers. While their plumage does contain preen oil, they have reduced water resistance compared to flying birds.
Chickens are a familiar example of a bird with imperfect waterproofing. Their feathers do contain preen oil and close-set barbs. However, chickens have only partially interlocking barbules such that their feathers are not perfectly waterproof. A wet chicken will thus try to shake itself dry and fluff its feathers to regain insulating air pockets.
Interestingly, some researchers have observed that heritage chicken breeds tend to have better water resistance than commercial chickens. This suggests that selective breeding for egg or meat production has led to chickens with plumage less suited to keeping them dry.
Do All Birds Preen?
Preening refers to when a bird uses its beak to distribute the preen oil secreted by its uropygial gland onto its feathers. Most birds have a uropygial gland and engage in preening behavior. Preening maintains healthy, flexible feathers and is vital for waterproofing.
However, there are a few exceptions. Some birds, like cormorants and turkeys, have only a vestigial non-functioning uropygial gland. Cormorants make up for this with extra oily secretions from their skin to coat their feathers. Turkeys on the other hand have very poor water resistance.
Birds like parrots, pigeons, and doves also lack a functioning uropygial gland. They rely on dust baths to maintain their plumage. Dust provides abrasion to remove old feather oils and replace it with oils from the environment. Studies show dust baths help maintain feather structure, flexibility, and water repellency.
Finally, some flightless birds like ostriches, emus, and cassowaries have no preen gland at all. They depend on infrequent dust bathing and the inherent water resistance of their feather structure. However, their feathers are still far less waterproof compared to most birds.
Do Bird Feathers Eventually Lose Waterproofing?
Yes, birds’ feathers do gradually lose their waterproofing over time. Feathers become worn and damaged through everyday use and exposure to dirt. The preen oil also degrades over time. That’s why preening to continually coat feathers with fresh oil is so important.
During molting cycles, old worn feathers are replaced with new ones. Molting timing and patterns vary across species. For example, waterfowl shed and replace their wing feathers sequentially over the year so they can still fly during molting. Other birds may have just one or two major molts per year.
Molting restores waterproofing, however some birds may become temporarily vulnerable to water saturation during the molt. For instance, a partially molted duck with some new feathers and some old worn ones may have difficulty staying dry in the water.
Can Birds Waterproof Their Feathers Artificially?
Birds in zoos and waterfowl sanctuaries sometimes receive applications of artificial waterproofing materials to their feathers. These synthetic waterproofing products temporarily improve water resistance.
Artificial sprays or powders containing oils, silicones, or polymers are designed to mimic the effects of natural preen oil. However, most experts recommend using them sparingly. Over-use may damage feathers or inhibit a bird’s natural waterproofing behaviors.
These products are sometimes needed for specific purposes like allowing a rehabilitating water bird to swim before its natural waterproofing is fully restored. But in general, regular preening is a better long-term way for birds to maintain their feathers.
Do Bird Nests Need To Be Waterproof?
Bird nests serve to incubate eggs and house hatchlings, so they must provide insulation and protection from the elements. Waterproofing is therefore an advantageous feature for many nests. However, the degree of waterproofing varies across species.
Nests in exposed locations high up in trees or cliffs generally need good weather resistance. Seabirds like albatrosses build sturdy nest mounds from mud, grass, and other materials that shield the eggs. Woodpeckers and other cavity nesters make nest holes in dead trees that are inherently protected.
Some arboreal songbird nests are cupped structures tightly woven from flexible grasses, moss, and even spiderweb. This weaving creates a sheltered interior. The exterior surface materials sometimes provide water resistance too. For instance, waxwings line nests with water-repellent wax crystals.
Waterbirds like geese and swans often build large nest masses right on the ground near water. These bulky nests rely more on insulation from eggs being buried in plant material for protection rather than waterproof exteriors.
So while waterproofness is helpful for many exposed nest locations, birds can also site nests in protected areas or construct them primarily for insulation rather than exterior water resistance. The key is keeping eggs and young dry inside.
Conclusion
To summarize, most birds have waterproof feathers specialized for their habitat and lifestyle. Preen oil to condition feathers and the microscopic structure of feathers work together to repel water in species ranging from seabirds to songbirds. However, some groups like flightless ratites and domestic chickens have lower feather waterproofing.
All birds need to periodically renew feather waterproofing through preening and molting. While supplemental artificial waterproofing products exist, these are generally just temporary measures. Overall, birds are elegantly adapted to maintain the waterproofing their feathers need to stay dry and insulated in their natural environments.