The Egg
Before we discuss candling, let's take a look at the anatomy of an egg. We all
:"kind of" know because we all eat chicken eggs... and a pigeon egg is
basically the same but smaller. The embryo grows inside the egg and
actually surrounds the yolk, using the yolk for nutrition as it grows.
The air cell gets gradually larger, the yolks get smaller and the embryo grows
larger as incubation proceeds. When I was studying a species of wild
birds I found that I could determine the day of incubation by measuring the
air cell diameter.
Why Candle
But of course, all of this wonderful miracle of life goes on inside the shell.
So we need a technique to peek inside. This is important because 1. some
eggs are not fertile, 2. some eggs get infected and should be removed from the
nest, 3. birds will continue to sit on "bad" eggs when they would lay more if
the "bad" ones are taken away. All of these reasons will help your
bottom line and success of your breeding.
How to Candle
The basic idea is easy. Shine a bright light through the egg to
illuminate the inside. There
are many "candlers" on the market to purchase, but you can make a very
effective candler quite easily. I begin with the brightest light
available.. My favorite is a LED spotlight, but you could make one from a
light bulb or other type of flashlight. The brighter it is, the better.
Then make a shield to pinpoint the beam through the egg and not into your
eyes. One might place a bulb inside a shoe box, or just use a piece of
cardboard 6 to 8 inches square.
 cut
a hole about 3/4 to 1 inch in diameter for the light to shine through.
Then just place the egg over the hole and shine the light from the bottom up
through the egg. You will be able to see the inside of the egg!
When to Candle
I like to check to see if eggs are fertile at about 3 to 5 days of age.
If both are infertile, I remove them and let the pair re-nest. If one is
infertile, you must decide if it is worth it to let you pair raise just one
baby.
What it Means
A small reddish area with blood vessels extending away from the center will be
visible in fertile eggs. This is the embryo floating around the yolk, looking
like a huge red spider. If the embryo dies, the blood draws away from the
embryo and forms what is called a blood ring. The blood vessels will not be
visible and the egg is dead. A clear egg is infertile and you see only
the yolk.
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