Why do birds stand on one leg?

Great question. I never thought about it until you asked. Here is a great explanation of how they do it, followed by some theories about why they do it.

I feel they are just showing off.

Fascinating question! The resident parrot does that, sometimes it seems she is staying warmer as only one foot is on a perch and she’s a bit fluffed. But I see her on one foot in warm weather too.

It’s a classic balance exercise and part of some yoga rituals.

It is a way to rest one leg at a time and birds also have the ability to turn off one side of their brain to sleep, one side sleeps while keeping the other eye open to watch for predators.

Lol, @gailcalled I never knew birds were into yoga!

Ditto @Coloma. Some birds are susceptible to foot diseases, injuries and pain, also. The rest helps prevent this.

Indoor/caged birds need a flat perch or flat area to stand on to rest and stretch their feet, otherwise they are more susceptible to disease and injury.

They have to stand on at least one leg or they’d fall over and then they’d be sitting

^^or levitating, aka flying.

@Coloma That makes total sense that they’d want to rest one leg or the other for long periods.

@SpatzieLover “Indoor/caged birds need a flat perch or flat area” That depends on the bird. It is especially true for ground-dwelling seed eaters. Tree-dwellers, like a parrot, might never need a flat perch.
Parrots even have evolved one of the front toes around to the back so they have two each in front and back, zygodactyl feet, making them more balanced for branch perching.

Actually @dabbler parrots in cages not only need to flatten their feet at times, they also require different sized perches to flex their foot muscles to prevent strain injuries. If you notice caged parrots clinging to the sides of their cage (especially true at pet shops), it is often to rest their feet from same sized cage perches.

@SpatzieLover Indeed, they do like a variety of perches.