Skip to content

Warm bird nests

The quality of a nest is essential to the development of future chicks. From the police weaver, which flirts with its nest, to prehistoric birds, a brief overview of a few avian maternities.

Let’s immediately dismiss an idea that is sometimes received: no, birds do not sleep in a nest; the nest is used to hatch the eggs and raise the chicks. And nests, on the planet, there are almost as many as there are species, nearly 11,000. Each has its technique, its particular needs. The ornithologist Jean-Marc Pons gave us an appointment in the gardens of the National Museum of Natural History (MNHN) in Paris to present some of them to us.

Let’s start with one of the most sophisticated, spectacular. In the shape of a sock woven not of wool but of plants, this nest is the work, as its name suggests, of the police weaver, a yellow and black sparrow found throughout sub-Saharan Africa and Mauritius and Reunion.

A nest of love

Among the weavers, it is the male who weaves, who builds the nest. Because the nest serves to attract the female. So he puts all his ardor and all his talent into it. And because he’s polygamous, he builds some every season.” between ten and twenty, says Jean-Marc Pons. Nests of a rather large complexity which is based on weaving. It’s not at all a shapeless heap, it’s structured. The bird will cut out strips of vegetation. It can be palm leaves or grasses. Then it will intertwine them according to a well-established plan.” To give a nest about twenty centimeters high, protected from bad weather, which one would think was made by human hands, suspended from the branch of a tree, the entrance being made from below and leading to the bedroom .

The weaver’s nest is an object of desire. Once his work is done, the male displays to attract the female. She enters the nest, inspects it, and if it suits her, the couple will form. But if the nest is rejected, the male will not try to pass it on to another; he will go so far as to destroy it. ” It is believed that the quality of the nest, the way it is built and whether it is well laid out, is a clue to the female of the quality of the male in question. », explains Jean-Marc Pons. What is love about? To the beauty of a nest…

A cozy nest

But most of the time, among birds, it is the female who builds her nest. It is she who will spend a few days to a few weeks there (depending on the species), the time to hatch the eggs and raise her offspring before they take flight. So you need heat for the maturation of the embryos first, then to protect the chicks born most often with a very light down.

A nest is necessarily cozy, like the one made in Europe by the goldfinch, lined with spider silk to provide insulation. The swallow, on the other hand, uses feathers as a mattress, whereas the silver-billed tanager is a little less comfortable, which furnishes its nest with simple animal hair. Inhabiting the tropical zones of South America, it does not have to fear the freshness of European spring.

From top to bottom and from left to right: a nest of silver-billed tanager, swallow, goldfinch, police weaver. F.GUIGNARD/RFI © Florent Guignard/RFI

A nest before

It takes heat for the eggs to hatch, and the first birds on Earth, descendants of the dinosaurs, did not incubate their own, because they were then heterothermic; what are falsely called cold-blooded animals, whose body temperature varies according to the ambient temperature.

The nests of these prehistoric birds (some 100 million years ago) were real incubators. ” Since the female could not brood her eggs and bring her own body heat to allow the development of the embryo, these birds made heaps of vegetation in which the female laid her eggs, and it was the heat brought by the fermentation which allowed embryos to develop “, explains Jean-Marc Pons, who works in particular on the evolutionary history of birds within the Institute of systems, evolution, biodiversity of the Musém national d’histoire naturelle.

A durable nest

Nests, in general, are single use. Except, for example, swallows’ nests, which are built to last. Houses of masons made with pellets of mud, which will grow in size over the years.

Woodpeckers are allies of biodiversity. Famous for their pecks in the trunks of trees, woodpeckers dig their nests in wood, which will then be squatted in the following seasons by other species of birds and even a mammal, the squirrel. An altruism that sometimes benefits from the involuntary support of a mushroom. “ Woodpeckers can dig quite deep, up to several tens of centimeters, and they sometimes speed up the process by inoculating this fungus into the tree, so that the wood is more easily worked.. This is timely.

THE QUESTION OF THE WEEK

“Do all birds nest in trees? »

No, raptors, for example, nest in rock cavities. And some birds, which cannot fly, are forced to nest on the ground. This is the case of the kakapo, a green parrot from New Zealand. Without a predator, the kakapo lost the use of its wings. Without predators until the arrival of Europeans, with their dogs, their cats, and rats (because before colonization, there were no mammals, apart from bats). Since then, the population of kakopos has collapsed… There are only a little over 200 left today.

A stork's nest.
A stork’s nest. © CC0 Pixabay/Rolanas Valionis

.

Leave a Reply

Your email address will not be published.