This is known as brooding, and they take turns doing it to ensure that the eggs are kept at an optimal temperature.

Helping birds near you - The RSPB Wildlife Charity

A nest box or other suitable nesting material should be provided to encourage courtship and breeding. Additionally, a diet rich in fresh vegetables, fruits, and nutritious seed mixes should be provided. Provide the perfect nesting place for a wide range of birds with this nearly indestructible nest box, featuring a 32mm entrance hole. Made from an incredibly tough and durable mix of sawdust, concrete and clay, this nest box is made to last. Features a removable front panel for inspection and cleaning. After the first egg is laid, she may start to incubate them immediately. However, some hens will wait until all eggs have been laid before beginning to incubate. This means selecting birds from different pairs or lines of descent and with at least three generations of unrelated birds.Tie the wire to secure it in the box. Now, you can just untie the wire and take the box’s lid off whenever you want. Two males may engage in courtship behavior, but no eggs will be produced. Two females may lay eggs, but they will be infertile. Once he has finished his display, the female may respond with similar behaviors or remain still in acceptance. Some parent birds seem determined to nest on the bare floor of the nestbox, and will throw out the litter until they reach the bottom of the box. In cases like this it is useful to put something under the litter that will prevent them from digging all the way down, and when they reach this material they will usually give up on trying to get rid of the litter. A piece of cardboard will serve this purpose – tear off one side to expose the corrugated inner layer, place the cardboard on the bottom of the box with the corrugations facing up, and cover with litter. Other materials that can be used for this purpose are AstroTurf and coconut fiber mats normally used to line plant baskets. This is the third such nesting box I have bought. I have bought other nesting boxes in the past but these made from a tree trunk have been the most successful. These nesting boxes make the perfect gift."

How to Build a Nest Box for Birds - Woodland Trust

The cage should be kept in an area of the house that receives natural light, such as near a window.Fertile eggs will have red spider-like veins, with a dark spot in the center and white space indicating an air cell is present at the wider part. Remember the formula for circumference: pi (3.14) x the circle’s diameter. So to get a circumference of 3, you will need a diameter of 95 inches, rounded up to 1 inch. 3. Put the sides and bottom of the box together with nails.