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Because birds live outdoors, there's an assumption that they're dirty and harbor many insect pests among their feathers. But this is very wide of the mark: Birds are as clean as cats, spending almost as much time grooming themselves as our feline companions do.

In the bird world, feather grooming is called preening, with birds bringing their feet and beaks into play to keep their feather coat in top condition. Birds spend a great deal of time each day waxing and aligning their feathers and picking off pests. In fact, preening and feeding are the two major activities in a bird's day.

Birds tend to preen away from public view, so we may not notice it. But a friend who'd been photographing an eagle nest recently observed an adult bald eagle engaging in lengthy bouts of hygiene:

"The eagle spent 52 minutes the first day and 57 minutes the next time I watched, and she went through every single feather, even the little ones. It's amazing what good care they have to take of themselves," Phyllis Terchanik said. Luckily she took some great photos of the eagle grooming.

A bald eagle
A bald eagle

Phyllis Terchanik

Why is it so important for birds to take care of their feathers? Feathers perform so many functions for a bird and work best when they're in top form. Birds bathe and groom to remove dirt that might interfere with their feathers' ability to warm or cool their bodies. Spreading oil from their preen gland helps keep feathers waterproof and supple. Preening also holds parasites in check and keeps flight feathers functioning at peak performance. And being well-groomed keeps a bird attractive to other birds.

You've seen birds at your birdbath, gleefully tossing water onto their backs and shaking themselves in the basin. But I have to admit I've never observed the aftermath, when a bird engages in oiling its feathers, spreading around the special liquid from a gland located under the tail. Apparently, they rub the gland (called the uropygial gland) to accumulate oil on their head and beak, then stroke it onto their feathers.

Barn swallow preening.
Barn swallow preening.

Jim Williams

Birds brush by so many things in a day, like leaves and branches and bird feeders, and their feathers get pushed and pulled around. This requires work, because feathers don't just fall back into the correct alignment. Birds run their feathers through their beaks to "zip" parts back into place. This is the job that takes up the most time in a grooming session.

Consider that a bald eagle has about 7,000 feathers, a trumpeter swan has 25,000 and even a tiny hummingbird has about 1,000. That's a lot of feather work. And they do it over and over again, every single day around the calendar.

St. Paul resident Val Cunningham, who volunteers with the St. Paul Audubon Society and writes about nature for local, regional and national newspapers and magazines, can be reached at

Feather count

Smaller birds tend to have fewer feathers:

Ruby-throated hummingbird: 1,000

Chickadee (summer): 1,000

Mourning dove: 2,600

Bald eagle: 7,000

Mallard: 12,000

Trumpeter swan: 25,000

Mallards have 12,000 feathers to tend to.
Mallards have 12,000 feathers to tend to.

Jim Williams