One of the greatest miracles of life i feel is how an egg transforms into a bird in a matter of weeks. My aim in this section is to provide you with a brief understanding as to what happens to the egg whilst being incubated.
When an egg is laid, embryonic development has already stared the growth is then delayed until the correct conditions are provided. At first all the cell are the same or at least very simler, but as the embryo grows cell differences can be seen. Some of the cells may be vital organs others become wings or legs.
Soon after the start of incubation begins, a pointed thickened layer of cells become visible it is from this point that the head and back bone start to develop. Blood islands start to develop and these latter become the vascular and blood system. The eye also begins to form.
on the second day of incubation the blood islands begin to link up with each other and start to form the vascular system, whilst this happens other cell are producing the heart. after 44 hours of incubation the heart and vascular system join and the heart starts to beat.
After the third day the beak starts to form and the limb buds of the wings and legs form
From here on the embryo grows rapidly. By day seven the digits appear on the wings and feet making the embryo more bird like. By the tenth day the beak has become hard and feathers are starting to develop. On the fourteenth day the bird’s claws have developed and the young birds starts to position itself inside the egg ready for hatching.
After 21 days the development of the embryo is complete and the chicks starts to escape from its shell. The chick starts to push is way into the air sack. The allantoids that have served as lungs start to dry up as the chick takes in air. The chick continues to push up and using the hard horn (egg tooth) on the end of its beak starts to cut into the shell. The chick then rest for a while then changes position and once again starts to cut into the shell of the egg. The chick keeps cutting until its head falls free of the open egg. All that remains then is for the chick to kick free from the rest of the egg. Exhausted the chick rest for a while and the navel openings heal and dry up and its down also dries.
Incubation and hatching is complete the young chick soon gains strength and begins to walk round. After a few days the egg tooth falls off.