Egg Laying

By Lindsey Keck

How do birds know when to lay eggs?

The average hen lays 250 to 270 eggs a year. Eggs take about 24 to 26 hours to form inside a hen. About 75 billion eggs are produced in the United States each year, which is about 10 percent of the world's total.

What other parts of the ecosystem are affected by the change in egg laying?

An egg shell is made of calcium carbonate, which is also the main ingredient. The shell makes up 9-12 of an egg’s total weight. It allows oxygen in and carbon dioxide out. The color of an egg yolk is determined by hen’s diet. The other colors within an egg vary with its age and other factors. Eggs are about 105 degrees Fahrenheit when laid. As they cool, the liquid inside contracts, and an air cell forms between these two layers at the large end of the egg, according to the Iowa Egg Council.

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