Bird nests are not for sleeping? I was surprised after reading this!

When most people think of a "bird nest," they probably think of a cozy little nest for birds to sleep in. However, bird nests are not actually built for birds to sleep in.

1.What is a bird's nest used for?

So, what is a bird's nest?

A bird's nest is actually built by birds during the breeding season to lay eggs, hatch and raise young birds.

There are many benefits to building bird nests. For example, bird nests are often built in clever locations, making them difficult for predators to find. Some birds build their nests between dense branches or hidden in cracks in rocks. For example, rock martin (Ptyonoprogne rupestris) chooses small grooves on steep cliffs to build their nests, which can help them avoid predators. They usually use mud as the main nesting material, and sometimes add some grass, feathers, etc.

Moreover, the material and shape of the bird's nest can help maintain a stable temperature and help the young birds grow in different weather conditions. For example, the barn swallow will build a bowl-shaped nest with mud and hay on the wall or eaves of a building. Mud has good thermal insulation properties, which can keep the temperature in the bird's nest relatively stable, preventing overheating at high temperatures and preventing the temperature from dropping too quickly at night.

Some birds also build sturdy nests that can keep eggs and hatchlings safe from wind and rain. For example, American Robins build bowl-shaped nests with a mixture of branches, grass and soil. This combination of materials provides a sturdy support structure to ensure that the nest can withstand the pressure of the growing weight of the chicks, and can also effectively protect the chicks from strong winds and rainfall.

2. Are there any birds without nests?

Yes, in fact, there are quite a few. For example, the bustard (Otis tarda) generally chooses to dig a shallow pit in the grass as a place to lay eggs and hatch them. Although they do not build a nest, they usually use the surrounding vegetation for simple covering, such as hay and leaves, to increase the insulation effect of the eggs and enhance their concealment to avoid being discovered by predators. [1]

Emperor penguins (Aptenodytes forsteri) do not build nests either, but incubate their eggs by placing them between the adult bird's feet and abdomen. The female penguin immediately hands the eggs over to the male penguin after laying them, and goes to the ocean to find food, leaving the male penguins to incubate the eggs collectively at the breeding grounds, and bring back food when the little penguins are about to hatch.

Some birds do not build their own nests, but choose to lay their eggs in other birds’ nests. This is the “dove” in the story of “the dove taking over the magpie’s nest”, the cuckoo (Cuculus canorus). The cuckoo does not build its own nest, but lays its eggs in the nests of other birds, letting the other birds help it hatch and raise its chicks. Sometimes the young cuckoos are larger than their host parents and are cared for. [2]

So, in fact, birds only build nests during the breeding season. Normally, birds do not do this specifically during the non-breeding season. At this time, their main activities are foraging and finding habitats. They will wander in a wider area to find enough food to maintain their energy needs. In this process, birds still need to find a safe place to spend the night and avoid danger. They may use natural habitats such as tree holes, rock crevices, bushes, etc. For example, the sparrows we often see in cities will choose building gaps, under the eaves, and branches and bushes. The temperature in these places is relatively stable, which can provide sparrows with a good warm environment.

3. Since bird nests are not specifically used for sleeping, where do birds sleep?

Most birds prefer to spend the night on safe and high branches. They can sleep while standing, and their unique body structure allows them to hold on to the branches firmly, ensuring that they do not fall.

Birds have well-developed hind limb muscles, and some flexor muscles in the tibia help the bird's toes grip branches tightly. When a bird grips a branch, the flexor tendons will tighten due to the downward pressure of its weight, allowing the bird to automatically grip the branch tightly. Only when the bird lifts its body and the intertarsal joints stretch, the four toes can loosen their grip. [3]

Birds also have a unique sleep pattern called unihemispheric slow-wave sleep, which allows them to rest in an alert state, with one half of the brain resting and the other half alert. Some birds can even sleep while flying, such as the frigatebird (Fregata).

Niels Rattenborg of the Max Planck Institute for Ornithology in Seewiesen and his international colleagues measured brain activity in frigatebirds as they flew, using air currents to glide, with their heads still and their wings stopped flapping. When turning right, the right eye remained open; when turning left, the left eye remained open. At the same time, EEG recordings showed brief slow waves, which should be due to hemi-brain sleep flight. Sometimes, they also entered a full-brain sleep flight state, in which their heads drooped and twisted, and the EEG recorded waves consistent with sleep on land, but this phenomenon occurred very rarely. [4]

References:

[1]https://www.forestry.gov.cn/c/www/dzw/150448.jhtml

[2]https://tv.cctv.com/2019/09/20/VIDEmo8lQfwTsdhRSCz8xCe0190920.shtml

[3]https://life.scnu.edu.cn/biology/jingpin/dwx/course_learn/chapter_18/chapter_1/learn/default.htm

[4]https://www.cdstm.cn/gallery/hycx/qyzx/202112/t20211202_1060760.html

The article is produced by Science Popularization China-Creation Cultivation Program. Please indicate the source when reprinting.

Author: Wu Qiong (popular science creator)

Reviewer: Huang Chengming, Researcher, Institute of Zoology, Chinese Academy of Sciences