Avian incubation facts for kids

Incubation, sometimes called brooding, is the special way birds help their eggs hatch. It usually means a parent bird sits on the eggs to keep them warm and safe.

Most of the time, the parent bird's own body heat warms the eggs. But some birds, like the Megapodes, use heat from rotting plants or even the sun! The Namaqua sandgrouse lives in hot deserts. To keep its eggs cool, it stands over them and shades them with its wings. The air's moisture is also super important. If it's too dry, the egg can lose too much water, making it hard or impossible for the baby bird to hatch. As the egg gets closer to hatching, it usually gets lighter, and a small air pocket inside gets bigger. This happens because some water evaporates from the egg. During this time, parts of the eggshell dissolve, and the calcium from the shell helps build the baby bird's bones.

Scientists have studied great tits and found that female birds move their eggs around. This helps make sure all the eggs get warmed evenly.

Bird Incubation: How Eggs Hatch

Parents' Roles in Incubation

How birds share the job of incubating eggs is different for each species.

• Female does it all: Often, the female bird does all the incubation. Examples include the Atlantic canary and the Indian robin.
• Female does most: In some cases, like with falcons, the female does most of the work.
• Both parents take turns: For birds like the whooping crane, both the male and female take turns sitting on the eggs.
• Male does it all: Sometimes, only the male bird incubates. This happens with cassowaries.
• Shared but different: The male mountain plover incubates the first set of eggs. If the female lays a second set, she incubates those herself.
• Helpers: In hoatzins, some birds (mostly males) even help their parents incubate later sets of eggs.

Incubation Time for Eggs

The incubation period is the time from when a bird starts sitting on the eggs until the young birds hatch.

• Shortest time: Some small passerines (songbirds) and cuckoos can hatch in just 11 days.
• Longest time: The wandering albatross and the brown kiwi can take up to 85 days! However, their incubation is sometimes paused. The emperor penguin has the longest continuous incubation, lasting 64 to 67 days.
• General rule: Smaller birds usually hatch faster. But there are exceptions. Birds that nest in holes or cavities often have longer incubation periods.
• Energy drain: Incubating can be very tiring for parent birds. Adult albatrosses can lose a lot of weight each day while incubating.
• Special cases: Megapode eggs can take 49 to 90 days to hatch. This depends on the nest mound and how warm it is outside. Even for other birds, the outside temperature can change how long incubation takes.

When Do Baby Birds Start Growing?

Baby birds inside the egg don't start developing until incubation begins. Freshly laid eggs from chickens, ostriches, and other birds can be stored for about two weeks if kept cool (under 5°C). Some sea birds can even pause development for longer periods.

Birds also have different ways of hatching their young:

• Hatching at different times: Some birds start incubating with the very first egg they lay. This means the chicks hatch one by one, at different times.
• Hatching mostly together: Other birds start incubating after laying the second egg. This can mean the third chick might be smaller if there isn't enough food.
• Hatching all at once: Some birds wait until they have laid all their eggs before they start incubating. This makes all the young birds hatch at the same time.

Incubation Periods for Different Birds

Here's how long some common birds incubate their eggs: