Why do some chickens lay green, white or brown eggs?
The colour of egg a chickens lays is entirely determined by the genetics of the bird and is inherited from one generation to the next. Chickens lay different colour eggs through selection, either of shell colour, pigment or both.
Egg colours can be mixed by cross breeding chickens. Olive eggers for example are a cross between chickens that produce an egg with a green shell and brown pigment.
What is the difference between the egg colours?
There is no difference in the egg or it's contents, only in the colour of the shell. In a blind taste test none of my friends or family could tell the difference between any eggs they were given.
It was one of my customers for eating eggs, as opposed to hatching, that asked me this morning after she had a look in the carton and was surprised by some really dark maran eggs and some green cream crested legbar eggs.
Below: A 3 egg display at a poultry show.
As a new convert to farm eggs she had only seen store eggs which for her have been a dark cream colour.
Aside from the colour of the shell there is no difference in eggs.
What colours can chicken eggs be?
The shells of chicken eggs can be:
- Reddish brown,
- Deep brown
- Light blue,
- A blend of any of the above colours.
It is always determined by the breed or genetics of the chicken that laid the egg. The colour of the egg can fade during the season, my Barnevelder eggs get lighter towards the end of summer and different birds of the same breed can lay slightly different eggs.
Like every other egg laying animal the shell colour of a chickens egg is the product of hundreds of thousands of years of evolution. Although they had a common ancestor the green and blue egg layers are very different from the chickens we know of that descended from the jungle fowl of Asia.
It was the need to keep eggs hidden from predators that gave rise to the colour of the egg and our selection and breeding of birds since that has given us the variety we know today. The patch of skin around the ear or lobe can be used to predict egg colour.
Below: A selection of multicoloured eggs.
All chicken eggs except green and blue start out in the hens oviduct as white shelled. If there is no extra pigment in the oviduct, such as in the breed, Leghorn, the final egg will have a white shell. The difference you see is all in the shell colour, the egg inside is the same.
For brown eggs, the colour of the egg shell is the last part of the egg production process when a brown pigment in the oviduct tints the outside of the shell. When you break open a brown egg, the outside of the shell is brown, but the inside is white.
For blue and green eggs, the pigment is deposited throughout the shell making process and these shells are uniform in colour throughout the whole shell.
If you use a scouring pad you can actually wash the colour off a brown egg but not a green or blue one!
For olive coloured eggs, the hen has genes for both the blue and brown pigments. The egg is first tinted blue as in the previous paragraph, but as it reaches the end of the laying process a coating of brown pigment is applied to the shell which creates the olive green colour.
Whether an egg is organic or not has no bearing on what it will look like.
White or cream egg breeds:
There is a simple way to tell white egg layers, look at the colour of the earlobe. As a rule that is valid in most cases chickens with white earlobe patches lay white eggs. Feather colour is not an accurate indicator of egg colour and brown/red leghorns still lay a white egg.
Below: 6 eggs from leghorns.
Breeds of chicken that lay white eggs include:
Probably the best known of the white egg birds is the leghorn and the modern hybrids it has spawned. These are responsible for around 80% of US eggs in stores. White and light egg layers are more common and more productive than dark egg layers.
My La Bresse Gauloise lay a really nice white egg but they are technically a meat bird.
Brown egg breeds:
As a rule chickens with red earlobes will lay dark eggs. The shell varies in colour from a chestnut brown to a really deep colour like the Marans eggs. Brown eggs may be speckled.
The shell colour gene passes through the female line and not so much the male unless it is green or blue. For this reason when I created my olive egg layers I used an Araucanas cockerel over a Barnevelder hen.
I have seen it suggested that brown egg laying hens are larger and more expensive to feed and that is why the eggs cost more but this is not the case at all. Brown egg laying hens lay fewer eggs than their white egg cousins and this is why they are more expensive.
Below: These beauties won first prize for Marans eggs at the national poultry show.
The deeper the colour the less eggs they lay. In really dark egg birds it may be as many as 50 or 60 a year less than a white egged chicken.
Welsummer, Barnevelders, Marans, Pendescenda and Croad langshans ( technically this is a purple egg because of the bloom). I have only included the dark brown egg layers here and they are almost without exception large fowl. Very few bantams lay dark eggs.
The darkest eggs I have seen are laid by the heavy Black Pendesencas (they are the only meat breed that lays these dark eggs and they mature quickly), followed by the Wheaten Marans for dark colour.
The Black Penedesencas also can lay a deep pink egg, that is a dark brown shell with paler coating to give a deep pink coloured egg.
The Welsummer eggs are pretty also, with a shiny finish and darker speckles.
Some people keep their hens not just for the colour of the nice yellow free range yolk, but for the Rainbow of egg colours!
Generally the darkest laying egg breeds are:
- Penedesencas from Spain
- Marans from France
- Welsummers from the Netherlands
- Barnevelders also from the Netherlands
There are a great many birds that lay a light brown egg like the Australorp.
Below: Deeply coloured egg require good selection at breeding time.
Green or blue eggs:
There are also Araucanas and Americaunas that lay blue and green shelled eggs. They also like the brown egg layers tend to lay slightly fewer eggs because the shells are just that tiny bit thicker.
Presumable there was some evolutionary advantage to slightly stronger shells. Green and blue eggers have red earlobes by default although there are exceptions but they are rare like female ginger cats.
- Ameraucanas-Many pure bred colours, black, silver, wheaten, blue, lavender, buff. Much rarer and best bought from a breeder should lay blue eggs only
- Tufted Araucana-A smaller less vigorous bird with extremely cute ear tufts, lay blue only.
- The cream crested legbar lays a green egg and I have German Bush Fowl which lay the most amazing blue egg.
The olive eggers is not a breed but a cross between two chickens, a dark egg hen and a green or blue egg male. Often need to be produces as an F1 or first generation cross as they do not breed true.
The egg colour follows the dam or female line except for blue and green so the dark component should be supplied by the hen. A suitable cross would be an Araucuana hen and a Marans cockerel.
Below: An olive egg.
As the facial feathers of the Araucuana are dominant they can be seen in the offspring but the feathers are often black or red or both. Mine are a cross between a Black Ameraucana and a Black Copper Marans, so they’re solid black with the trademark Ameraucana cheek feathers. The eggs tend to be a little smaller and the hens not so productive so it really is a labour of love to breed them.
A vigorous type of non-standard Ameraucana brightly coloured and variable, easily found from hatcheries. Easter Eggers are not a breed per se, but another crossbreed that does not conform to any standard but lays large to extra large eggs that vary in shade from blue to green to olive to aqua and sometimes even pinkish.
This is the traditional lucky dip chicken that can be just about any colour, have any type of comb and lay almost any colour egg.
The display hybrid vigour and are usually quite productive.
Hybrid chicken egg colours:
Because of their highly bred and standardised nature the eggs from hybrids tend to be very similar as they are all practically clones of each other.
The common hybrid chicken in the UK is the highline/isa-brown/Warren type and they are a non descriptive brown medium sized chicken that lays a large and consistent egg. The egg colour for this type is normally a dark cream to light brown.
Leghorn hybrids are white egg layers.
There is a growing range of hybrids produced for the backyard environment that produce darker egg like the speckledy which is a Marans cross.
Does the diet effect the shell colour?
The diet has a minimal effect on egg colour. Egg colour fades over time both during the laying season and as the bird gets older but it is normally only a shade or two and gradual. It certainly won't change more than a shade or two if you alter the diet.
Proper diet helps hens lay eggs with good shells. High calcium use can mean hens need more than their body takes in - which can result in taking from minerals from bone. Calcium in the form of oyster shell is offered to many flocks because of this.
Is the yolk different in coloured eggs?
Some people say that brown eggs have a yolk that's more richly coloured than white eggs. Feeds vary and the more corn, fresh grass and coloured foods they eat the yellower and more coloured the yolks will be.
It is not the colour of the shell that predicts the the yolk but what the chicken has been eating and what breed it is. In my experience rare breeds lay nicer eggs with much more intense yolks that hybrids.
Commercially there are additives added to feed stuffs that deepen the yolk colour. These include marigold from the flowers and paprika and beta carotene from surplus carrots.
There is no benefit to any colour egg except your personal preference so choose the ones you want and be happy. Neither is any colour healthier than another, what makes eggs better is free range happy hens and a varied diet.
Is chickens skin colour and egg colour linked?
Skin and shell colour in chickens is not linked in any meaningful way. Both are characteristics that can be passed down and selected for in breeding but a white skinned bird will not lay a white egg for example. It might but may just as easily lay a brown egg.
Chickens also have different skin colours - yellow or white depending on breed with the exception of the silkie, with black skin. The breed characteristics are responsible for what coloured shell. Skin colour is a little more complex than this, if you remember the La Bresse I mentioned earlier it has a blue tint in the skin and bright blue legs.
Does feather colour effect the egg ?
Will a black chicken lay a dark egg for example. The answer is no, it might do but I have a black Andalusians that lay a brilliant white egg and White Marans that lay a deep chestnut egg. There is no rule about feather colour and egg colour.
Is there any nutritional difference in coloured eggs?
Depending on the breed, a hen will lay from 500 to 800 eggs in her lifetime. And whether an egg is brown or white, it’s still the same on the inside. They taste the same and are equally nutritious.
There is absolutely no difference in the nutritional value of coloured eggs. Although brown eggs are often thought to be more healthy as they look more "natural", there is nothing more nutritious about brown eggs when compared to any other variety. there is no taste difference between brown and white eggs either, try a blindfolded taste test to see.
How the shell is produced:
The shell is deposited on the egg as the last part of the process and it takes four to six hours to complete.
In fact all eggs (except green/blue) start out as white in their development and any colour change after is simply due to genetic factors. Brown eggs can cost more because they typically come from hens lay less eggs, and that cost gets passed on to you as the consumer.
Hens that lay brown eggs tend to lay fewer eggs over the year which is often why eggs in shops are white or light in colour. so if you want to save some money the go with the white variety.
Egg shells start to become thinner when chickens reach 80 weeks old, this is why commercial chickens are sent to slaughter at around the time. The hens are unable to produce enough calcium so calcium is used from the bones. Thinner eggs means more cracked eggs.
So white eggs aren't bleached and green eggs aren't rotten then?
These questions might make you chuckle but I have been asked them more than once.
They never bleach eggs although in some countries they are washed before they end up in stores and no, the green ones are not going rotten.
They will be washed in an antibacterial solution but it will not change their colour.
Where can you buy coloured eggs and how much are they?
It is becoming more fashionable for the higher end stores to sell eggs from rare breed hens and even Guinea fowls but as a rule you will need to find a chicken keeper or get your own hens.
You will probably need to find a chicken keeper or homestead that has pick and choose eggs to buy. There are a few smallholdings near me that sell lots of different types.