Telling a Story with Photos: The Uropygial Gland


This is a lot cooler than it sounds. Seriously. Birds have a specialized gland on their backs – technically, between the fourth caudal vertebrae and the pygostyle, that provides preen oil. And preen oil is what birds use to maintain their feathers. The amount of preen oil and the amount of preening varies from species to species. Water birds tend to use the most and to preen the most. Let’s watch a female Harlequin Duck engage in some serious preening.

Here’s your basic Harlequin Duck female. She decides she needs to preen.

Harlequin Female - Ready to Preen

Harlequin Female – Ready to Preen

Now a bird doesn’t have hands, paws or any means to apply preen oil except their heads. So one of the motions you see most often when a bird is preening is the head rubbing the lower back.

First, get some oil from the Uropygial Gland

First, get some oil from the Uropygial Gland

Depending on where the bird wants to apply the oil, they will smear the preen oil on a different part of their head. Here, she is smearing the preen oil on the right side of her head. She then applies the oil to her coverts.

Applying preen oil to covert feathers at the top of her wings

Applying preen oil to covert feathers at the top of her wings

She next applies the preen oil to the end of her bill to preen the feathers of her breast.

Applying preen oil to the breast, where water washes to away most quickly

Applying preen oil to the breast, where water washes to away most quickly

Of course, you have to stop and look around pretty often, because a bird that fails to pay attention to its surrounding becomes a meal for, say, a Bald Eagle that might be hanging around.

Does that Bald Eagle over there look hungry?

Does that Bald Eagle over there look hungry?

Part of preening involves shaking the feathers out, a sort of stretch and partial flapping of the wings. The idea is to line up the interlocking barbules of the feathers.

Coming down the stretch

Coming down the stretch

And now, with the feathers a bit more water-resistant, and all properly sorted out, it’s time for a late snack.

This looks like it might be tasty

This looks like it might be tasty

All these photos were taken at Solomon Gulch Hatchery, on the easterly side of Port Valdez, Alaska on the evening of July 19. WC thanks this pretty little hen for her cooperation and wishes her well over the winter.

Remember: the Uropygial Gland. Indispensable to birds everywhere.1


  1. Well, technically some “primitive” birds do just fine without one. Those include kiwis (Apterygidae), emus (Dromaiidae), ostriches (Struthionidae), rheas (Rheidae), cassowaries (Casuariidae), mesites (Mesitornithidae), bustards (Otididae), pigeons and doves (Columbidae), amazon parrots (Psittacidae), frogmouths (Podargidae), and woodpeckers (Picidae). But how they cope will have to be the subject of another post. 
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