Chickens eggs come in all kinds of colours
– white, brown, pale creamy colour. We have some with spots. We even have blue ones. But
no, even in Scotland they don’t get tartan eggs.
So what makes the colour? And do we get brown eggs from brown chooks, and white eggs from
white chooks? No matter what the colour of the egg, it’s
really just a white egg with a coating on the outside – either a smooth coating or
a coating with a few spots and speckles in it. Or like this one, it looks like even brown
on one end but there’s spots and speckles on the other end.
If you look inside a white egg, you can see that it’s white all the way through. If
you look inside a brown egg, you can see very clearly that actually it’s white inside.
The brown egg is just a white egg with a brown coating on the outside.
It takes about 26 hours for a hen to make an egg and most of that time is actually spent
making the shell. And only during the last couple of hours is the brown coating put on
the outside. The brown coating comes from a substance called protoporphyrin, which is
related to a substance called haemoglobin. Haemoglobin is of course the substance that
makes our red cells red. Whatever colour eggs a hen lays, she lays
pretty much the same colour all the year round – that’s her colour egg, although it does
tend to get a bit paler as the season wears on. You can see this in the colour of the
eggs that my two hylines lay. My two hylines are both the same age – about two years
old, and to start with they both laid eggs that were this dark brown colour. But as time
went on, the eggs got paler and paler, until now, one of my hens, Goodness, lays eggs that
are just about this colour. Shirley, however, took a break over the last winter, and didn’t
lay any eggs at all for about a couple of months. And when she came back on the lay
again, now she’s laying these dark eggs again. During the time that she took a break
from egg laying, she refilled her paint pot, and now she’s got plenty of brown colour
to put on her eggs again. So Shirley and Goodness are brown hens and
they lay brown eggs. And Gillette and Remy are white shavers, white hens and they lay
white eggs. And Margy, my buff laced Wyandotte, is kind of a creamy coloured hen and she lays
creamy coloured eggs. And as it happens, mylavender Araucana lays blue eggs. So do brown eggs come from brown hens and white eggs from white hens? Well, no, not exactly. But you
can get an idea of the colour of the eggs that a hen lays by looking at the colour of
her earlobes. Did you even know that a hen has earlobes?
They are those little bits skin on the sides of the chickens head.
For most of the breeds that we know well, a hen that lays white eggs will have white
earlobes. The white colour comes from a substance called purine that makes their earlobes white.
And a hen that lays brown eggs has earlobes that are red. The red comes from the colour
of the blood showing through – kind of like the inside of our mouths are red or pink.
This association between the colour of the earlobes and the colour of the eggs doesn’t
always work, because there is actually no genetic link between the genes for earlobe
colour and the genes for egg shell colour. Silkies have blue earlobes, but they are not
the ones that lay blue eggs, silkies just lay a white egg.
So what about those blue eggs? Fascinatingly, unlike the brown colour that’s just applied
to the outside of the egg, if you look inside a blue egg, you’ll see that the blue colour
goes all the way through. The blue colour is actually incorporated into the egg shell
when the egg shell is being made. The blue colour comes a from a pigment called oocyanin,
or oocyanin, I’m not really sure how to pronounce it. That’s a substance related
to biliverdin. You might not be familiar with the name biliverdin, but I bet you are familiar
with it – it’s the pigment that makes bruises look green or blue.
The hen adds oocynanin all the way throughout the production of the egg shell, and so the
blue egg is blue all the way through. If a hen that lays blue eggs also puts a brown
coating over it, the brown on top of the blue makes it look green.
It’s fun getting different coloured eggs in my nest box every day. That’s one of
the reasons I have different kinds of chickens in my garden.