Why do birds preen their feathers?

The story behind the answer

Birds preen to keep feathers clean, aligned, and functional. Using their beaks, they “zip” separated barbs back together and spread oil from the uropygial (preen) gland near the tail. This oil conditions feathers, adds waterproofing, and helps maintain insulation and flight performance, while preening also removes dirt and external parasites. In short: preen = pristine, protected plumage.

Context tip: Waterbirds rely heavily on preening to stay buoyant and dry; by contrast, cormorants have less waterproofing and often spread their wings to dry. Some birds even “ant,” rubbing ants on their feathers, possibly for parasite control. Remember: preening isn’t about color or beak sharpening—it’s maintenance that keeps the feather toolkit airworthy and weather-ready.