Re: How does a baby chick know to peck it's way out of an egg?

Hello,
The information on chick hatching was taken from the Avian Embryo site at 
http://www.msstate.
edu/dept/poultry/avianemb.htm
This site contains some in depth info on everything related to chicks 
hatching, but to get on with the answer we can begin with what is the 
normal position of the chick inside the egg. When it is time for the chick 
to hatch the head is in the large end of the egg,under the right wing, with 
the legs drawn up toward the head. If the head is positioned in the small 
end of the egg, the chick's chances of survival are reduced by at least 
one-half.
This is a serious malposition, or wrong position, for hatching. Just as a 
wrong position makes birth more difficult in mammals, a wrong position of 
the chick makes hatching more difficult, or impossible.

After 21 days of incubation, the chick finally begins its escape from the 
shell. The chick begins by pushing its beak through the air cell. The 
allantois, which has served as its lungs, begins to dry up as the chick 
uses its own lungs. The chick continues to push its head outward. The sharp 
horny structure on the upper beak (egg tooth) and the muscle on the back of 
the neck help cut the shell. The chick rests, changes position, and keeps
cutting until its head falls free of the opened shell. It then kicks free 
of the bottom portion of the shell. The chick is exhausted and rests while 
the navel openings heal and its down dries. Gradually, it regains strength 
and walks. The incubation and hatching is complete.
The horny cap will fall off the beak within days after the chick hatches.

If you would like a simpler explanation of chicks hatching, check out the 
following Site that details a kindergarten class that hatched their own 
eggs. http://lincoln.mi
dcoast.com/~wps/baston/chicks.htm


The following sites will give you information in regards to your other 
questions.
 http://www.ext.msstate.e
du/pubs/pub1182.htm http://www.mes.umn.
edu/Documents/D/I/DI0631.html http://www.openarmsmaga
zine.com/incubati.htm http://www.os
trichesonline.com/photographs/photo1.html

Hope you find this information useful, thankyou for taking the time to send 
in a 
question to the Mad Sci Network.

June Wingert
Baylor College of Medicine
Houston  ,  Texas