The chick inside the egg has fully developed its air sac, which is located at the large end of the egg.
The egg should be candled to check for any defects, such as blood spots or cracks.
The chick has grown and filled most of the egg, leaving only a small amount of space for it to move.
The eggshell should appear slightly translucent and it’s possible to see veins and shadows through the shell.
The chick is still getting its nutrients from the yolk, but it has also started to absorb the egg white or albumen.
The chick is preparing for hatching, which usually occurs between days 19 to 21 of incubation.