Smithsonian National Zoological Park l Friends of the National Zoo



Incubating Kiwi Eggs

In kiwis, only the male incubates the egg. Our male, Maori, is doing such a great job that he will be allowed to incubate for the first 30 days of the typically 68 to 78 day long incubation period.

After that, the egg will be put in an incubator where the temperature and humidity can be controlled.


We check the egg daily using a technique called "candling." We shine a bright light on the egg, which illuminates the interior so that the development can be monitored. First, the shape of the air cell is checked. If the egg is infertile it will begin to break down and the outline will appear very ragged. In a fertile egg, we see a clean line.

In addition, we mark and date the outline of the air cell with a pencil. As the embryo develops, the air cell grows larger. This gives us a good idea of how the embryo is developing.

Egg Weight

We will also weigh the egg to make sure its not losing too much weight as the embryo develops. An egg should lose between 12 to 16 percent of its fresh weight before it internally pips.

If the egg is losing too much weight, we will increase the humidity in the incubator by increasing the surface area of water in the trays or decreasing the level of ventilation (making sure the ventilation is not completely blocked).

If the egg is not losing enough weight then we will decrease humidity by reducing the surface area of water in the trays or increase the level of ventilation.