Britannica Sources used in this answer

How long do bird eggs take to incubate?

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A zebra finch (Taeniopygia guttata) with a bright orange beak, gray head, orange cheek patch, and black-and-white striped tail perches on a branch. — Bird A brightly colored zebra finch (*Taeniopygia guttata*) perched on a branch.

The incubation period for bird eggs typically ranges from 11 to 80 days. This duration depends on several factors, including the size of the bird and the developmental state of the chick at the time of hatching.1

For example, chicken eggs generally require about 21 days of incubation to hatch. While most birds actively incubate their eggs—often using a brood patch to transfer body heat—there are exceptions:2

Megapodes: These birds rely on external heat sources, such as decaying vegetation, rather than direct body heat.1
Brood parasites: Species like cuckoos and cowbirds lay their eggs in the nests of other birds, leaving the incubation duties to the host species.1