Birds hatch from eggs
Birds reproduce by laying eggs. When a female's ovum is fertilized, the bird embryo begins to develop almost immediately while the mother's body builds the egg around the embryo.
Facts
Most female birds have two ovaries when embryos, but only the left ovary develops into a functional reproductive organ. The exceptions to this rule are birds of prey (hawks, falcons, etc.), who develop both ovaries into functional organs.
Consideration
Cell division begins while the egg is forming. Once the egg is laid, embryonic development stops until proper cell development environmental conditions are met again through incubation. If this does not occur, the embryo will not develop.
Timeframe
Incubation varies among the different bird species and lasts from as little as ten days for the cowbird to eighty days for the royal albatross. Most of the embryonic development occurs during incubation.
Features
The first feature visible in an egg is a pointed, thickened layer of cells at the tail end of the embryo. This feature is the primitive streak, from which the head and backbone form. The cardiovascular system, beak, limbs and respiratory system appear next. The claws and feathers are the last to develop.
Fun Fact
In birds, the female egg determines the sex of the hatchling rather than the sperm of the male.
Tags: embryonic development, into functional