wsg@cbnewsk.att.com (wendy.grohol) (11/24/90)
While watching the birds eating in my window feeders this morning I remembered two small blue jays that came to dine yesterday. They looked very much alike and I wondered if birds have twins. I should think so but how does this work? Once a sperm enters an egg a chemical reaction changes the outer layer so no other sperm can enter. If something goes wrong and 2 sperm get in the egg what happens? What I'm really wondering is how identical twins would come to be. Can two embryos survive together in one egg-shell? Or can the egg split before the hard outer shell forms? How and when does the hard outer shell form for that matter? I had bio in high school and college and have seen lots of nature films but I have never seen anything on egg fertilization and shell formation in birds. Thanks, Wendy