What conditions are necessary for the development of an embryo in a bird’s egg? How is this achieved?

For the development of an embryo in a bird’s egg, it is necessary:
– nutrients – a large supply of nutrients is in the yolk;
– aquatic environment – the egg white plays the role of an aquatic environment;
– oxygen is needed – at the blunt end of the egg, the shell membrane leaves the shell and forms an air chamber for gas exchange;
– you need protection against drying out, the penetration of bacteria – it is provided by the shell, consisting of calcium compounds – they give the shell hardness and are a source of calcium for the bones of the skeleton.