Tuesday, May 1, 2012

Life in a Zoo: The Real Thing - How a Goose Hatches Her Eggs

I was amazed at how many eggs my geese were laying.  Several geese laid their eggs inside an abandoned doghouse. Apparently, it was prime real estate.

We were such novices in those days, and it was long before we ever owned a computer, much less had access to the internet.  So our resources on learning about our critters was limited. 

What I didn’t understand was that I should have taken some of those eggs.  But we left them all.  It didn’t take long before there were so many eggs in the nest that the goose couldn’t possibly reach the ones on the bottom, much less turn them several times a day as was needed.
Usually a bird will lay only one egg a day, depending on the species. Emus will lay one egg every three days. The bird will not begin to incubate the eggs until the nest is full. For some species, that may be two or three eggs, but for some birds, like the emu, they may have fifteen or twenty eggs in the nest.  Geese will usually lay about eight to ten.
There is one of God’s wonderful mysteries. So if a goose lays an egg a day for ten days, why is it that they all hatch on the same day? 

The egg is made of four main parts; the shell, the yolk, the membrane, and the albumen (white liquid).
The shell is a protective covering. Although it is porous, it keeps the developing chick safe and clean. 

Each species of bird has special requirements for incubation.  Some birds need a drier atmosphere, and some birds need a damper atmosphere. 
The only time an incubating goose will leave her nest is to go to the water. She bathes and fills her feathers with lots of moisture. This is essential for goose eggs to hatch. This moisture is absorbed through the shell.
The membrane surrounds the inside of the shell. It has tiny blood vessels in it.
The yolk is chock full of nutrients and proteins. That’s what the baby bird feeds on. It has a kind of umbilical cord from it’s naval to the yolk sack.
The albumen provides cushioning and protection for the baby bird.  As the chick develops, the albumen evaporates through pores in the shell.  As it grows, the chick displaces the liquid albumen.
Here’s the interesting part. The first eggs that are laid have very thick albumen, which evaporates slowly. With time, that thick albumen breaks down and gets thinner, so it evaporates more quickly. Those eggs laid at the end of the laying season have very thin albumen, ready to evaporate quickly through the egg.
The mother does not set on the eggs and begin incubation until the last egg is laid. By the time the last egg is laid, the albumen is about equal in all the eggs, so the chicks develop at the same time.

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