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Saturday, April 20, 2013

Pips and Hatching

"Pipping" refers to the process of the chick initially breaking through the shell, using a hard projection on its bill called the egg tooth. The resulting hole is the "pip" that the chick then enlarges to finish hatching. 
Source: FAQ: Red-tailed Hawk Cam on allaboutbirds

Cornell RTH Cam_04222012_Ezra_Eggs_137p
#1 and #2 Eggs Pipping on April 22, 2012
Screenshot by elly012912

Other Information About Hatching:

As development proceeds, the egg loses water (as water vapor) through the shell. Moderate water loss in this way creates an air-filled space in the blunt end of the egg, where the chick draws its first breath before breaking through the shell. By the time the chick is ready to break out, the eggshell is considerably thinner than it was when first laid. This is because the calcium from the eggshell is incorporated into the skeleton of the developing chick.

As hatching nears, the chick begins calling softly from inside egg. The mother answers the chick and remains on or very near the nest during this critical period. The chick begins chipping away at the inside of the eggshell with a small, hard bump on the tip of its bill. This "egg tooth" falls off shortly after helping the chick escape its confining shell. It often takes a red-tail chick a full day or more to open a small hole in the shell. After several more hours of work, the chick opens a hole large enough to break through to freedom.

Source:  Preston, Charles R. Wild Bird Guide: Red-Tailed Hawk. Mechanicsburg: Stackpole Books, 2000. Print.

One-day old Peregrine
Falcon Nestling
with Egg Tooth Visible

Other Information About Hatching (continued):

After incubation is complete, the young hawk must try to break out of the shell.  For this to happen the young hawk “grows an ‘egg tooth’ at the end of the upper mandible and develops powerful ‘hatching muscles’ on the back of its head and neck.” (Dobkin, D., Ehrlich, P. and Wheye)

As the young hawk comes to the end of development, the hawk would swallow the surrounding liquid in the egg and “pull the remaining membrane-wrapped yolk into its abdomen” (Dobkin, D., Ehrlich, P. and Wheye) The young hawk then continues to work its head and upper body into the airspace of the egg, where it can start to breathe air and peep. Then by contracting its hatching muscles, the young hawk forces the egg tooth against the shell wall, creating a small hole and uses its newly developed head and legs to move and force the egg to break to allow a nice and easy escape.  After several weeks, the egg tooth drops or wears off and the hatching muscles waste away.  


Source: http://bioweb.uwlax.edu


Grandad_Rufus: What’s Happening in Those Eggs?
Grandad_Rufus: Fact 1: A young bird's heart starts to beat around 72 hours after the start of incubation. At this time, the heart has only 2 chambers but will eventually divide into 4; two atria and two ventricles.*
Grandad_Rufus: Fact 2: Eggs are porous to the extent that they let O2 in and CO2 out. Since being laid, the egg has also been losing, through evaporation, very small amounts water through these pores, and as a result it actually weighs less than it did when it was first laid. The shell is becoming somewhat thinner as some of the calcium in the eggshell is being absorbed by the embryo and used to help build its developing bones.**
Grandad_Rufus: The hatching process starts with what is called draw down. The air cell at the large end of the egg gets larger and the embryo breaks through a membrane to enter that air cell.
Grandad_Rufus: Then within about 48 hours the embryo/chick breaks the egg shell (pip) with the egg tooth.
Grandad_Rufus: Then within the next 48 hours, the chick will have rotated within the egg (counter-clockwise) to break the shell and push the top off. This is called breakup.
Grandad_Rufus: Young are born with an internal food source called a yolk sac that acts like a supplement to feed the chicks.  


* Source: http://www.wvec.com/marketplace/microsite-content/Eagle-Cam-chat-session-with-Dr-Dave-McRuer-117607833.html

Posted by Grandad Rufus on April 3, 2013
See Blog Post on What's Happening in Those Eggs?