Quote Originally Posted by RandyRemington View Post
Paul, so after 25 33% chance possible homozygous animals in a row failed to prove did the breeder decide it's a homozygous lethal mutation? Did ya'll notice about 1/4 bad eggs from the het X het breedings or any infertile possible homozygous animals?
Yes, he decided crested was lethal when homozygous. The odds of getting that string of failures by chance was just too small. He also found that there were fewer crested zebra finches than normals from a crested x normal mating. This was when the results of many matings were totaled.

Part of what I did was to check the finch nests for eggs and nestlings. A clutch averaged 6 eggs. Three babies leaving the nest was considered good results. The other eggs were either infertile or dead embryos. Entire clutches might be abandoned. An egg was approximately 1/4 inch long, so hatchlings were tiny. Dead hatchlings were not recorded. They were lost in the nest material or litter on the cage floor. So we could not zero in on the stage of homozygous crested death. Sometime before feathering out was our best guess, which leaves plenty of time. Sterility in adults did not seem much of a problem.