unfertile eggs

Question
Hi,
My budgie has had her first clutch of 7 eggs[she does have a male with her] I have candled the eggs and a couple have red veins but the others just seem to be yellow inside! why are some fertile but not the others.she sits on them all the time[she is doing really well for a first time mum] Even though there are red veins in 3 of them what are the chance of there not being a baby in them?
Thank
Rachel

Answer
Hi, Rachel,

Be sure you are candling the eggs after they've been incubated 7-10 days.  If you candle too soon, you won't see anythng.  She has to have incubated them a week to 10 days for you to see any veins.  Some are fertile and some not because the male's sperm didn't reach some of the female's eggs, so they weren't fertilized.  Females can lay eggs without having mated, and all these eggs will be infertile.  It's hormonal activity that produces eggs.  When they mate, sperm fertilizes some zygotes and some don't get fertilized.  The more often they mate, the better chances of all eggs being fertile.  If there are red veins, this means a process has started inside the egg where a developing embryo needs a blood supply thus, the veins.  It is possible, however, during development that developing embryos die inside their shell never to hatch.  There are many reasons for this.

Chrys