Depends upon the avian species. Most common (farm wise) is the 18-28 day range, but a few are shorter and a couple are longer.
There is no definite age which you can no longer incubate a fertile egg, but the fresher an egg is, the better chance of a successful incubation and hatching.
Thirty days
21 days
Duck egg incubation can be from 27 to 35 days depending on the breed.
The incubation period for a hedgehog egg is around 35 to 58 days.
Egg incubation
The word "incubation" directly refers to the time an egg needs to be kept warm before it hatches. Since cows do not lay eggs, they do not have an incubation period. They have what is called a "gestation" period. This gestation period is generally 285 days long.
incubation
Tasmanian devils do not have an incubation period. The term "incubation" relates to how long an egg takes to hatch, and Tasmanian devils do not lay eggs. The gestation period of the Tasmanian devil is between 18 and 21 days.
All reptile eggs need incubation to hatch.
Incubation of a kiwi egg takes 70 to 80 days.
depends on the animal