Apr 19 2013

How Do They Hatch?

Published by at 7:30 am under Bird Anatomy,Tenth Page

Chicken hatching in incubator (photo by grendelkhan on Wikimedia Commons)

In the next few days the peregrine eggs at the University of Pittsburgh are going to hatch, so now’s a good time to explore…

How does a baby bird get out of the egg?   It’s a strenuous one to two day process in very tight quarters.

  1. When a chick is ready to hatch, he pulls himself into the tucking position with his beak sticking out between his body and right wing.  This gives him the leverage he needs to whack at the shell.
  2. The chick then breaks through the membrane at the large end of the egg that isolates the air sac and he breathes for the first time.
  3. Next he starts to bump the shell with the curved ridge of his beak where he has a calcified egg tooth that’s sharp enough to crack the shell.
  4. His strenuous hammering is aided by the hatching muscle on the back of his neck.
  5. While still in the egg he communicates with his parents and siblings by peeping and pecking sounds.  The parents know which eggs are alive because they’re speaking.  The siblings know their brothers and sisters are ready to emerge.  In precocial species, which must all hatch at once, the chicks listen to each others’ tapping to coordinate the hatch.  Elder chicks tap slowly, younger ones tap rapidly so that all of them reach the finish line in a 20-30 minute window.
  6. Finally the chick cracks his shell all the way around.  He pushes with his feet and the egg splits open.  His mother moves the shell away and he lies quietly, waiting for his down to dry.

After hatching the chick’s specialized tools aren’t needed anymore.  The egg tooth falls off (in songbirds it’s absorbed) and the hatching muscle shrinks into just another neck muscle.

Watch the National Aviary falconcam for hatching at Dorothy and E2’s nest.  The streaming cam is blurry but it is broadcasting sound so you’ll be able to hear the chicks peeping inside their shells.  That will be our first sign that hatching is underway.

 

(Credits: photo of a chicken emerging from its egg from Wikimedia Commons.  Click on the image to see the original.  Today’s Tenth Page is inspired by page 460 of Ornithology by Frank B. Gill.)

One response so far

One Response to “How Do They Hatch?”

  1. Chrison 19 Apr 2013 at 12:21 pm

    Terrific detailed information! Thanks again and again, Kate!

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