Birds can lay eggs of rainbow hues ranging from pure white to lavender, yellow, mint green, orange and blue-green.
Some eggs can even come with spots, specks, blemishes, and other markings.
Why does the color of eggshells vary in nature? Yes, camouflage is probably the foremost reason for brownish and more earthy shades, but why blue?
Read on to find out which birds lay blue eggs (hint: it’s not just bluebirds) and the possible reasons behind this bright color.
Some Birds That Lay Blue Eggs
You probably already know that bluebirds lay blue eggs. Although those in North America like the Eastern, Mountain, and Western Bluebird lay pale blue to white eggs, you’re not likely to discover these eggs quickly.
They’re cavity nesters and will very rarely lay their eggs outside of a cavity – except when desperate. Also, about 4-5% of bluebirds actually lay white eggs!
But not to worry, hundreds of other species of birds lay blue eggs you’re far more likely to happen upon.
Those who do find blue eggs in strange locations are most likely seeing an American Robin egg. House Finches also have eggs that are bluish-green and may use a nestbox.
Starlings also lay blue eggs, but you will be able to easily see the difference because they are bigger than bluebird eggs.
Here is a list of some of the most well-known birds that lay blue eggs.
- Red-winged, Rusty, and Tricolored Blackbird
- Blue-footed Booby, Bluethroat, Blue-gray Gnatcatcher, Blue Grosbeak, Blue Mockingbird
- Gray Catbird
- American, Fish, Hawaiian, and Tamaulipas Crow
- Snowy Egret
- American, Lawrence’s, and Lesser Goldfinch
- Cassin’s Finch, House Finch, Oriental Greenfinch
- Great Blue Heron, Little Blue Heron
- Common Myna
- Aztec, Bicknell’s, Clay-colored, Dusky, Swainson’s, Varied, White-throated, and Wood Thrush
- Bay-breasted, Olive, and Yellow Warbler
- Eurasian Jackdaw, Eurasian Bullfinch
- Blue jays
- Eastern, Western, and Mountain Bluebirds
- House finches
- Red-winged blackbirds
- Snowy egrets
Reasons Why These Birds Lay Blue Eggs
Female birds have two’ ink cartridges’ in their reproductive system: biliverdin and protoporphyrin.
All birds possess these two molecules, but not all species use it.
The ones that do use it, however, produce beautifully colored eggshells.
Biliverdin is the molecule that produces the blue and green pigment in eggshells.
The higher the concentration biliverdin, the bluer the egg.
Protoporphyrin is the pigment that makes eggs red or brown or creates visible spots and speckles on the eggshells.
These ‘inks’ are added to the freshly formed shell in the last few hours of production.
Interestingly enough, the color of the eggs will change through the laying cycle of birds that lay multiple eggs at a time. It is as if they’re running out of pigment, but in actual fact, it points to the mother bird running out of calcium and nutrients.
Since 10% of the calcium in eggshells comes from the female, she needs extra calcium and nutrients while laying eggs. If she doesn’t get any, the eggs will vary in shade color.
So, now that you know how it works let’s move on to why it is necessary.
A lot of animals in the wild are colored to blend in their surroundings. If adult animals need it to escape from predators, fragile eggs need it even more. There are a lot of hungry predators out there looking for a quick snack.
But, camouflage doesn’t really apply to blue eggs. It’s the eggs with neutral tones and markings that blend away into the nesting material.
If birds lay eggs out in the open in a scrape nest or directly on the ground in open areas, camouflage is especially important.
To add an additional layer of protection, these birds will often decorate their nests as well as a form of concealment.
Okay, this may make you go ‘huh?’ but bear with me. Eggs are delicate, and the radiation and heat from the sun can easily cause harm not only to the shell but also the chick.
The darker the egg, the better protected it will be against UV radiation, but, on the flip side, the quicker it will heat up and possibly cause the death of an unhatched chick.
A lighter egg has less chance of overheating but is more exposed to UV radiation.
Because of the connection between eggshell color and UV radiation and heat buildup, birds need to strike a balance between the color of their eggshells and the environment.
For example, birds that lay their eggs in an exposed area will likely have lighter-colored eggshells. Eggs laid in areas sheltered from the sun will most likely have darker hues.
As you can imagine, the process will take many generations to perfect.
To recap, a study done to determine the function of different hues of eggshells found that pigments serve to reduce them:
- Damaging ultraviolet radiation
- The infrared radiation that heats the inside of the eggs
So to keep it simple, blue and other pigmented eggs regulate the effects of sunlight on the embryo/chick.
Some Other Eggshell Color Clues
We now know that the color of eggs gives us a clue about the amount of sunlight that reaches the bird’s nest. But the color of eggshells can also give us some other important information.
The health of the mother bird and chicks
The brighter the eggshell, the better the health and diet of the mother bird. This means the hatchlings will also be strong and healthy.
Nest care habits
Typically, heavily camouflaged eggs are left unattended for longer periods as parent birds go forage. The more plain and noticeable eggs, in contrast, will be carefully guarded and watched by parents and thus have less need for camouflage.
If there is a dramatic difference between eggs in the same nest, it can indicate a brood parasite.
Birds like Brown-headed Cowbirds and common Cuckoos lay their eggs in nests of other birds to be raised as foster chicks.
So, if there is an egg that is much larger or smaller than the rest or has a different color in the brood, it is most likely from a brood parasite.
What About Patterns, Spots, and Blotches on Blue Eggs?
Speckled eggs are just another form of camouflage. You usually won’t find patterns, spots, and speckles on cavity nesters like the Eastern Bluebird, but open nesters and ground nesters are a different story.
Ground nesters such as ducks, geese, shorebirds like Avocets, Plovers, and Sandpipers, game birds including Turkey, Pheasant, and Grouse, as well as other species like Bobolink, Wood and Hermit Thrushes will lay speckled eggs.
To guarantee the survival of their eggs, they rely on well-hidden and camouflaged eggs to make a predator’s job more difficult.
Other than camouflage, a study done at the University of Oxford found that blotches on eggs serve an additional function. That is to strengthen the eggshell.
According to Andrew Gosler, Oliver R Connor, and Richard Bonsor, the pigment-related molecule protoporphyrin mentioned above also strengthens the eggshell.
The pigmentation compensates for any calcium deficiency and helps harden especially the inner parts of the egg.
We have to mention that this study only presented preliminary findings but that no direct relationship between eggshell strength and protoporphyrin pigmentation has previously been noted. There are mountains of circumstantial evidence, however.
Lastly, the spots and speckles on eggs can be used for identification. Remember those clever birds too lazy to build a nest or raise their young? The ones that lay their eggs in other birds’ nests?
Well, if the patterns on eggs differ from species to species, it will be easier to spot such egg trickery!
Observing Blue Eggs In A Nest
Sometimes we as bird enthusiasts can get so excited when we stumble onto a bird’s nest. We want to investigate and identify what bird species we’re looking at, and that is perfectly fine, within limits.
Observing the nest and the comings and goings of the mother bird and her partner is more than fine. But one thing you do not want to do is disturb.
We know it’s tempting to want to touch or handle the eggs, maybe even snap a quick picture.
But can you imagine in what panicked state the mother bird is when you go poking around in the nest and touching her eggs?
You’re a mighty big predator, and she doesn’t know if you plan on having her babies as scrambled eggs for breakfast or if you’re just inspecting the pattern on the egg.
Even though you’re a curious birdwatcher, there are signs that will give you hints as to what type of bird’s nest and egg you’re looking at. There’s no need to touch the egg or disturb the nest.
Look at the size, shape, color, markings, and finish of the eggs to guide you in the direction of the species of bird in question.
Also, small birds lay small eggs, while large birds will lay larger eggs. All these clues will help you narrow down the species of bird.
There’s an unwritten rule under birdwatchers to observe but not involve yourself. Stick to that rule and the mamma bird and her eggs will be safe.
There are actually laws in North America that forbid the destruction of birds’ eggs and nests, as well as the sale of any bird eggs.
However, if it is a fledgling, leave it where you found it. You will be able to distinguish between a nestling and a fledgling by not only the fluffiness but also the fact that a fledgling will be able to grip your finger.
The fledgling phase takes place before the first flight, so the bird’s parents are most likely nearby looking after it. Don’t interfere in this process.
Bird eggs are as distinct as the birds themselves, and blue eggs only form a small part of the colors you can expect to see.
Birds are capable of laying eggs in different hues of white, tan, turquoise, teal, brick-red, and even pink!
Even the textures and coatings differ. You’ll find some dull eggs while others will be shiny; some will be bumpy and others smooth.
Then, of course, you may even find some Jackson Pollock-worthy spots, specks and blotches on some eggs. Mother nature can be a real show-off, right?
Of course, these patterns aren’t just for camouflage, they also strengthen the eggshell and make it possible to identify any brood parasites.
Scientists are still searching for more precise answers. Just think what other reasons may be behind the blue tones of birds eggs, or the specks and blotches?
In the next ten years, we may know much more about this subject. The more we understand about birds, eggs, and how the environment and natural selections impact them, the better we can help conserve our feathery friends.
Frequently Asked Questions
Let’s look at some other questions that may have popped into your mind about birds and their eggs.
1. What birds lay eggs on the ground?
Ground-nesting birds like ostrich, emu, tinamou, and pelicans lay their eggs in a scrape, while shorebirds like terns, gulls, and puffins all nest on the ground.
Some penguins like gentoo penguins also nest on the ground.
Ducks, geese, and swans also make their nest on the ground because their young are capable of walking and swimming straight after hatching.
You will also find weak fliers like quail, pheasant, and partridge nesting on the ground.
2. Are tiffany blue and robin egg blue the same?
Robin egg blue is also called eggshell blue or lost egg blue. It is a greenish-blue color similar to the shade of egg laid by the American robin. Tiffany blue is a more light-medium tone of robin egg blue.
3. Is robin egg blue the same as teal?
Robin egg blue and teal are both shades of cyan – one of the subtractive primary colors. Both hues have a greenish-blue tint, but teal is darker than Robin egg blue.
4. What breed of duck lays blue eggs?
Magpie and Ancona are two types of ducks that lay blue eggs.