In Victorian times, making collections of birds eggs was very popular and easily understood.

Then it was the only way to explore this aspect of natural history.

These days we have all this information at our finger-tips and I cannot understand why some people carry on the egg-collecting practice, although there is still a ready market for the sale of rare birds.

These days most of us have digital cameras to “collect” them instead, but care should be taken not to disturb the incubating birds.

The development of the egg is of great interest. The egg starts to form in the female’s oviduct. She first produces the watery jelly-like substance we call egg white or albumen.

This surrounds the yolk which contains the fertilised combination of a female cell and sperm. The whole egg is then surrounded first by protective membranes and later a chalky and ever hardening shell forms.

In order to develop eggs are incubated by the parent bird.

In some cases the birds pluck feathers out of their bellies to create the brood patch - an area of warm blood vessels to transfer body heat to the eggs.

Many eggs are pear-shaped especially with ground birds such as lapwing.

These shapes when laid in groups of four make the prefect contact with other eggs and thus conserve heat. The eggs are also perfectly camouflaged so that they are hard to see on the ground.

Other birds especially the song thrush have beautiful eggs coloured blue with spots.

Here camouflage does not matter because the nest is in deep cover.