After 5 days inside the home-made incubator, I could see streak of blood inside the egg. I thought it was a ring of blood of a dead embryo, but when I happened to video-document the matter, I was surprised to see the beating heart of the budgie's embryo.
The egg candling was done by using a flashlight, diskette film to separate the light and a bulb reflector as the holder of the egg.
This egg was the only one saved out of the 3. The rest were broken by the parent because I touched and changed the nest box beddings.
Photo:
Video at:
http://www.youtube.com/watch?v=-DJJm4UTBQg
May 16, 2011 UPDATE: Unfortunately the egg did not fully developed. After 15 days, I did not see any heart beat anymore and I noticed that much fluid were inside the egg, instead of solid particle. I think this failure was due to unregulated temperature and frequent egg handling.