Why Do Baby Birds Jump Off a Cliff

Why do these birds throw themselves off cliffs?

The Arctic murre has a curious habit of flinging themselves out of the nest before information technology is quondam plenty to fly. Now scientists know why.

When young murres abound to nearly one quarter of the size of an developed, they suddenly throw themselves off the towering cliffs that they call home. They plunge headfirst, hundreds of metres towards the ocean in what at first glance appears to be a suicide attempt.

Merely, information technology is non. New research suggests that it is in fact a sensible and spectacular survival strategy.

Murres wings are adapted for diving and they are poor fliers, so they need to limit the corporeality of energy used when searching for food for their young.

Instead of flying between the sea and their nest high upwardly on the sea cliffs, they take their young with them to ocean, so that the young murres are always alongside their dads.

Scientists have long wondered why young murres throw themselves out of their nest before they can even fly or fend for themselves. (Photo: Shutterstock)

"We have long wondered about this special behaviour. At start glance, information technology doesn't look like it's an evolutionary advantage to let the fragile young birds throw themselves from a tiptop, downward to the sea amid the rocks and the waves. But our study helps explain this," says Morten Frederiksen, from the Section of Bioscience at Aarhus University, Denmark.

The study is published in the scientific journal, The American Naturalist.

New insights into a previously unknown activity of murres

The new study casts light on a part of the murres' life that scientists take known relatively lilliputian near until now, says Tone Kristin Reiertsen, who studies bird behaviour at the Norwegian Institute for Nature Research (NINA). Reiertsen was not involved in the new study.

"We know very petty virtually what happens from when they leave the nest to when they come back to the breeding ground, three or 4 years later. The reason is that information technology'southward difficult to report the birds when they alive their lives out at sea," says Reiertsen.

A male murre keeps his chick close by. The young swim and dive into the sea, simply are not even so able to grab their own food. (Photo: Lars Maltha Rasmussen)

"The males and young birds are especially vulnerable in this menses where they sometimes drift through oil drilling and shipping areas," she says.

What happens to them in that menstruum can influence the unabridged murre population. So the new report provides of import insights into this crucial period, says Reiertsen.

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A unique bird

Near other birds apply one of ii strategies: either young birds stay in the nest until they are fully grown and can fly, or they follow their mothers, similar hens and ducks.

The next step for scientists is to study murre's behaviour during the rest of the year, to see why populations are shrinking. (Photo: Shutterstock)

The murre'south trick of leaping out of the nest, frequently bumping against the steep cliffs equally they fall to the water below, is totally unique.

"It'south really unusual behaviour. The immature cannot cope on their ain. They cannot fly, they cannot find food themselves, and predators such as gulls and foxes view them as a delicious meal. Why don't they but stay put in relative safe on the cliffs? This is the question that we've long asked ourselves," says Frederiksen.

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They relieve energy by feeding immature at sea

To respond this question Frederiksen and his colleagues equipped 14 adult murres with pocket-size data loggers on, so they could see how the birds behaved before and later the young threw themselves from the nest.

Murre birds

Murres are a species of large auk and weigh effectually ane kilogram.

They live in the northern hemisphere where prefer to nest on the sides of steep cliffs.

Murre can swoop up to 200 metres depth in the body of water to hunt for food.

Females lay but 1 egg during the mating season.

The males take care of the chick when they leave the nest.

Females accept care of the nest when their young leave.

The young birds accept a thick layer of feathers and soft downwardly on their stomachs, which cushions their fall from the cliffs to the ocean.

The small data loggers collected data such every bit air force per unit area and temperature, and the bird'south location.

This allowed the scientists to see when the birds dived into the sea to feed, and where they swam to.

They saw that the males dived much more often after the young birds had left the nest.

"When the immature starting time leave the nest, information technology's up to the males to feed them while the females remain at the colony to mate with other males and have intendance of the nest. When the immature birds end up in the feeding footing, information technology means that they no longer take to fly back to the colony to feed their young, and they tin can therefore collect more than food. Moreover, murres are not very good flyers. We scientists accept a joke that they wing marginally better than penguins, then it uses a lot of energy to bring food back upward to the nest on the cliffs," says Frederiksen.

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Males need to be with their young

In comparing with the females' fishing grounds, the males often feed in areas that are relatively poor in the types of crustaceans and small fish that they usually catch.

This is because the males stay close to the young, and are therefore express as to where they can fish. The females meanwhile, are free to fish wherever they like.

But still, the males were able to feed their chicks twice equally often at sea than both parents were able to do past flight back and along between the colony and the sea.

"In this style it makes sense that the young birds go out the nest, despite the risks. We can also see that autonomously from during the actual spring, few murre chicks die in the period after leaving the nest," says Frederiksen.

During this period the male person birds moult their flight feathers, which prevents them from flying away and forcing them to stay with their chicks.

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Possible explanation of declining murre populations

In that location millions of murres around the world, simply their populations are in decline.

The new insights into their behaviour could help to explain this tendency. So, Frederiksen and his colleagues take launched a new research project to written report the murres' behaviour during the residue of the year.

"It could exist that they have problems with finding nutrient or something similar. This is what we'll investigate at present," says Frederiksen.

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Read more in the Danish version of this article on videnskab.dk

Translated by: Catherine Jex

Scientific links

• Variation in Growth Drives the Duration of Parental Intendance: A Test of Ydenberg's Model, American Naturalist (2017), DOI: x.1086/691097

External links

• Morten Frederiksen
• Tone Kristin Reiertsen

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Source: https://sciencenordic.com/animals--plants-denmark-videnskabdk/why-do-these-birds-throw-themselves-off-cliffs/1445536

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