14 Extraordinary Bird Egg Facts

Learn interesting egg facts, including what bird lays pink eggs, what bird lays eggs in another bird's nest and why bird eggs aren't round.

Bird Eggs Are Similar to Dinosaur Eggs

One of the most interesting bird egg facts that despite the broad variety in colors and markings displayed by bird eggs, just two pigments are responsible for staining the shells of all known species of living and extinct birds, including dinosaurs.

Learn how to identify bird eggs by color and size.

Cowbirds Are Nest Thieves

juvenile cowbirdCourtesy Julia Worth
Chipping sparrow feeding a young cowbird

Female brown-headed cowbirds deposit their eggs in other birds’ nests. Cowbird eggs have been found in nests of more than 220 other species.

Do birds reuse their nests?

How Strong Are Eggshells?

sandhill crane eggsCourtesy Rissy Medlin
Sandhill crane nest, eggs and baby

Large birds sit on eggs, too, so their eggs have to be strong enough to withstand the weight. It takes about 26 pounds of pressure to break a swan egg.

Learn when bluebirds nest and lay eggs.

How Much Does an Ostrich Egg Weigh?

High Angle View Of Ostrich With Eggs On FieldKasper Nymann / EyeEm/Getty Images
Ostrich female protecting the big eggs in the rain

Here’s another one of the most amazing egg facts: a single ostrich egg can weigh as much as 5 pounds. Psst—this is the only bird nesting material you should put out.

What Kind of Bird Lays Dozens of Eggs in a Nest?

egg facts Male and female wood duckEEI_Tony/Getty Images
Male and female wood duck on a nest box 

A wood duck can lay up to 15 eggs in one nesting attempt, but a single nest may have as many as 40 eggs from more than one female.

Learn how to recognize northern cardinal eggs.

Hummingbird Eggs Are Tiny

Hummingbird nestCourtesy Marion Ball
A peek inside a hummingbird nest

Rufous hummingbird eggs are 1/2 inch long and fit snugly in the 2-inch-wide nest, which usually holds two eggs. Here’s everything you need to know about hummingbird nests.

How Long Does Egg Laying Take?

Robin eggsCourtesy Lesley Rutter
American robin eggs in a cup shaped nest

Most songbirds lay one egg per day until their clutch is complete. Learn more about mourning dove eggs and baby mourning doves.

What Bird Lays Pink Eggs?

tree swallow bird houseCourtesy Carol Pedersen
Tree swallow family in a birdhouse

Pale pink at first, tree swallow eggs turn white within four days. Learn more about swallow nests.

Do Birds Peep Before Hatching?

American white pelicans lay two eggs per clutch. The young are able to squawk from inside their eggs if they’re too hot or cold. Check out super cute photos of baby birds.

Why Are Bird Eggs Not Round?

egg facts, Killdeer Standing Over Nest With EggsJoe McDonald/Getty Images
Killdeer standing over nest with eggs

An egg that is pear-shaped easily settles within the nest, or even on bare ground if the parents opt not to build a nest. Learn about the different kinds of bird nests and how to spot them.

Some Birds Can Recognize Their Own Eggs

egg facts Cowbird Egg Among Bluebird Eggs in a NestLois_McCleary/Getty Images
Cowbird egg in a clutch of eastern bluebird eggs 

Eggshell colors serve to signal the identity of each egg. For example, the parasitic brown-headed cowbird egg sticks out in the nest among an American robin’s blue eggs. Typically, the robin recognizes the cowbird egg and tosses it out.

Discover how orioles weave elaborate nests.

Eggshells Help Baby Birds

bluebird eggs and hatchlingCourtesy Heather Parker
Newly hatched baby bluebird and eggshell

The eggshell serves as a calcium supply for the growing embryo. As the embryo matures, the shell slowly becomes thinner and the hatchling has an easier time breaking through.

Can you move a bird nest?

California Condors Don’t Have Many Eggs

California Condor sitting on a rockWeili Li/Getty Images
The California condor is the largest bird in North America. They are endangered species. 

Endangered California condors wait until they’re 6 to 8 years old to find mates, then produce only one egg every one to two years.

Oldest Egg Laying Bird

This last one of our egg facts might be the most amazing! Wisdom, a 70-year-old Laysan albatross and the oldest banded wild bird on Earth, hatched an egg in 2021 with the help of her mate, Akeakamai.

Next, get ready for baby birds with these tips for nesting season.

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Lori Vanover
Lori Vanover is the senior digital editor for Birds & Blooms. She has a bachelor's degree in agricultural and environmental communications from the University of Illinois. Lori enjoys growing vegetables and flowers for pollinators in her backyard gardens. She also is an avid bird-watcher.