Finding a blue egg in a bird’s nest can be a surprising sight. Many species of birds lay eggs with colors that camouflage well in their nests, like brown, white or speckled eggs. So what explains the vibrant blue eggs laid by some bird species?
Birds That Lay Blue Eggs
There are a handful of bird species that are known to lay bright blue or blue-green eggs. Some of the most common include:
- Eastern bluebird
- Mountain bluebird
- Western bluebird
- Eurasian blue tit
- Azure-winged magpie
- Fairy penguin
Of these, the three species of bluebirds found in North America are the birds most recognized for their striking blue eggs. The mountain bluebird lays eggs that are a sky blue color. Eastern bluebirds have eggs that are a slightly brighter, more turquoise blue. Western bluebirds lay eggs that are a more pale or muted blue-green.
Why Are the Eggs Blue?
The blue color of these eggs actually serves an important purpose. Pigments called biliverdins are responsible for the blue-green color. These pigments help filter sunlight and strengthen the shell of the eggs. This helps protect the developing chicks inside.
The biliverdins in blue eggs work similarly to the carotenoids that give other eggs their brown, yellow or reddish coloration. While the biliverdins filter light, the carotenoids help camouflage eggs against nest materials like grasses, twigs and soil.
Some research indicates that the biliverdins in blue eggs allow more light to pass through the shell than brown eggshell pigments. This may help embryos develop more quickly. However, more research is still needed on how exactly the pigments benefit development.
How Are Blue Eggs Formed?
Like all egg colors, the blue pigmentation comes from the mother hen. The biliverdin pigments are deposited onto the eggshell as the egg passes through the oviduct. The more pigment deposited, the richer the blue color.
Interestingly, the main biliverdin pigment found in blue egg shells is not soluble in water. This means that the blue color remains even after the egg is washed or exposed to moisture.
Some research indicates the color may continue darkening even after the egg has been laid. Exposure to light and oxygen may encourage the oxidation process that deepens the blue-green shade.
Do Other Birds Lay Blue Eggs?
While bluebird species are best known for their striking blue eggs, there are a few other bird species around the world that also lay blue eggs, such as:
- Fairy penguins – These small penguins native to Australia and New Zealand lay eggs that are a light blue-green color.
- Azure-winged magpies – Found in parts of Asia, these vivid blue and black birds lay light blue eggs speckled with brown spots.
- Blue-footed boobies – Their eggs are a pale blue-green or turquoise hue.
- Laughing gulls – This coastal gull has eggs that are a deep green-blue speckled with dark brown spots.
- Eurasian blue tits – This common European songbird is known for its bright blue eggs.
Some duck species like the Chilean teal duck also occasionally lay light blue eggs. However, blue eggs are highly unusual in most waterfowl, chickens, and other common domestic birds.
Are Blue Eggs Rare?
Overall, blue eggs are quite uncommon among wild birds. Only about 1% of all bird species have blue egg coloration. Most birds lay eggs in neutral colors like white, brown or buff.
This rarity indicates that blue eggs likely evolved selectively in a few specific lineages. The pigments probably gave an adaptive advantage to those species through light filtration or other benefits we don’t yet fully understand.
Within the species that do lay blue eggs, each female bird tends to be consistent in the coloration of the eggs she lays. However, there is some natural variation between different females’ eggs in the exact pigmentation and patterning.
What Do Blue Eggs Signify?
During the nesting process, blue eggs don’t necessarily signify anything specific compared to eggs of other colors. The blue is simply part of that particular species’ natural coloration.
However, blue eggs can sometimes indicate an egg was laid by a different female bird than others in the nest. For instance, tree swallows frequently lay eggs in each other’s nests. If a female tree swallow lays an egg in another’s nest, the blue color helps signal that the egg doesn’t belong to the nest’s owner.
For people who keep chickens or other pet birds, a blue egg in the nest when none have appeared before could indicate a wild bird is also laying eggs there.
Blue Eggs in Folklore and Culture
Due to their beautiful color, blue bird eggs have inspired many myths, legends and superstitions across cultures. Here are some examples:
- In Ancient Scotland, some believed blue egg shards had protective powers and placed them above doorways to ward off evil.
- An Appalachian legend claimed that a child would become a great singer if they were given a bluebird egg to suck on.
- Modern day Fantan players sometimes place bets on whether blue eggs will appear in a bird’s nest.
- A dream about blue eggs may symbolize creativity or a desire to become a parent, according to some dream interpretations.
- There are many Ukrainian folk songs mentioning bluebird eggs and their shine like precious stones.
Thanks to their appealing color, blue eggs are also used extensively as decorative symbols and in arts and crafts. Ostrich eggs are sometimes painted or dyed blue as novelty gifts or decorative objects.
Are Blue Eggs Safe to Eat?
The blue pigment biliverdin is not toxic to humans or birds. So blue eggs laid by chickens or wild birds are perfectly safe to eat. Their nutritional value is the same as brown eggs.
The blue color may fade somewhat when the eggs are cooked. But many people enjoy the novelty of blue chicken eggs for baking or eating plain.
In North America, the Ameraucana and Araucana chicken breeds are well-known for laying blue or blue-green eggs. Their eggs are a lighter blue than wild bird eggs. Backyard chicken keepers sometimes keep these breeds specifically to produce blue chicken eggs.
Conclusion
While most birds lay camouflaged eggs, several species around the world astound with their brightly blue eggs. These include bluebirds, blue tits and fairy penguins among just a few others. The blue or blue-green color comes from biliverdin pigments in the eggshell.
Scientists are still researching how precisely these pigments benefit bird eggs. But they likely help filter sunlight and strengthen the shell. This may aid healthy chick development.
Over the centuries, blue eggs have inspired many myths, legends, superstitions and cultural traditions. And they continue charming people today. Backyard chicken keepers enjoy blue laying breeds. And artists use blue eggs as subjects for paintings, crafts and jewelry.
While uncommon in nature, blue eggs remain absolutely safe for both wildlife and human consumption. Their rarity in the wild continues inspiring admiration and fascination with the select bird species that produce these jewels of nature.
