Why Do Shorebirds Stand on One Leg?
When you first walk through the Delaware Bay exhibit at the Zoo's Bird House, you’ll be struck by several sensations: the energetic cheeping of a rowdy flock, the briny smell of saltwater, a burst of humid air, and the sight of dozens of small, chunky birds crowded along the water’s edge.
As you observe this group of sandpipers, turnstones, red knots, sanderlings and plovers, you might notice a few of them are hopping around on one leg. It’s not uncommon for visitors to ask a keeper or volunteer if that bird is injured, or if it had one of its legs removed. Some might even come to the conclusion that the Zoo has an aviary filled with legless birds!
So, what’s going on? In short: the other leg is tucked under the birds’ feathers.
It’s worth noting that several birds in this exhibit came to the Zoo as wild rescues. These are animals that have been injured and rehabilitated and are otherwise healthy, but were left with a crooked wing or other condition that would prevent them from surviving in the wild. (Animal care teams make every effort to care for these unique animals and give them healthy lives—learn how the Zoo cares for animals with impairments.) But there are no one-legged birds in the Delaware Bay exhibit.
The Bird House is home to a rescued American golden plover. (Smithsonian/Roshan Patel)
If you’re wondering why some of them stand or hop around on one leg, you’re not alone. Science can’t always provide a clear answer as to why a bird chooses to behave a certain way. But based on our collective understanding about animal biology, there are a few possible explanations as to why the one-legged-tuck might be the right call for a bird:
1. They’re regulating body heat.
It’s a method of thermoregulation, or keeping the body at a stable temperature. Here’s how it works:
As the bird’s heart pumps warmer blood from the body’s core through the arteries and down into the leg, the blood comes into contact with a network of cooler veins pumping blood back up from the bird’s legs and toes. Traded heat warms up the blood in the veins before it leaves the bird’s body, removing the heat from the outflowing blood and keeping it from being wasted. The exchange of heat between warm arteries and cool veins creates a system where warm blood doesn’t leave the bird’s core.
This process of heat transfer is an adaptation called “rete mirabile,” which is Latin for ‘wonderful web.’ Scientists have observed it at work in a range of animals, from flamingos and herons to fish and even some mammals.
Can you spot the sandpiper resting on one leg? (Smithsonian/Skip Brown)
2. They're conserving energy.
Bird feathers are a lightweight, natural insulation that help a bird trap in body heat. (And they work fantastically: think about how winter coats are often filled with soft down feathers.) But the bare legs of a bird are uncovered, which means they’re exposed to the ambient temperature of their surroundings.
If a bird wants to reduce the amount of body energy it uses “heating” it legs, it can switch over to the one-legged stance. This cuts the amount of uncovered skin touching the open air by about half. Watch the bird long enough and you’ll notice it swaps legs occasionally to keep the “standing” leg warm.
In the Delaware Bay exhibit, many of the birds have evolved to spend part of the year living among the rocky beaches and windswept shorelines as far north as New England, Canada, and Alaska. These parts of the world get cold even in the summer breeding season, which is why our Zoo shorebirds naturally incorporate these heat-saving adaptations into their daily routines.
The Delaware Bay exhibit at the Bird House. (Smithsonian/Skip Brown)
3. They're taking a break
Small shorebirds like sandpipers tend to be active and full of energy. They zoom through their coastal habitats, dashing along the water’s edge to probe in the sand while avoiding the crashing waves. If you ran around with the energy of a plover all day, your leg muscles would get pretty tired by the end! For shorebirds, the one-footed hopping technique might be a way to give the tired leg a rest while still retaining the ability to move around.
About the Bird House
The Bird House exhibit invites visitors to explore the fascinating world of migratory songbirds, waterfowl and shorebirds native to North, Central and South American ecosystems. Bilingual panels—in English and Spanish—tell the story of how migratory birds connect communities and contribute to healthy ecosystems across the Americas. Visitors can also learn about the Smithsonian Migratory Bird Center, the only scientific institution solely dedicated to understanding migratory birds.
Part of the Smithsonian’s conservation efforts include connecting animals like migratory shorebirds with millions of guests each year. Discover how you can help save species. Plan your visit today.
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