"Black sun"

Hundreds of thousands of birds gather when flocks of starlings merge in order to rest in the reed forests of the Wadden Sea. The largest flocks might even completely envelope the low evening sun. This unique phenomenon is called black sun.

Black sun is one of nature's most wondrous phenomena. Year after year, it astounds people who experience it for the first time. Even people who are familiar with it lose themselves in the rhythmic and unpredictable movements of the starlings. Each individual starling is merely a black dot in a constantly shifting pattern that whirls across the night sky and creates enormous shapes that can fill the horizon and even block out the sun. As an enthralled spectator, one stares in wonder at the starlings and the energy they expend shifting around the flock. For the starlings, though, it is completely natural and necessary. The black sun phenomenon occurs when flocks of starlings gather to spend the night in the reed forests of the salt marshes. The shifting movements are a defence against birds of prey.

The best hunters attack

When the birds gather, there are many eyes to spot any potential danger, while the dizzyingly large flocks confuse attacking predators. The starlings are often attacked by the fast and agile sparrow hawk. However, they also face attacks from merlins, hen harriers, marsh harriers and goshawks. Even the world's fastest animal, the peregrine falcon, will sometimes enter the fray to put starling on the dinner menu. Starlings create the phenomenon of black sun in order to avoid being eaten by some of the best hunters in the sky. The movements become no less dramatic when birds of prey enter the picture.

The reed forest protects starlings

The reed forests are located in the most sodden areas of the salt marshes. Foxes and other terrestrial predators won't go out there, as it would entail plodding through mud and water. Birds of prey are not a concern at night, as they rely heavily on their eyesight when hunting. Starlings can therefore spend the night dry and in safety between the reeds.

Starlings don't collide

One wonders how starlings are able to move so quickly in the sky, in such close formation, without colliding with each other. Starlings have no special sixth sense to make this possible. On the other hand, they are equipped with extraordinary reflexes that are almost 20-times faster than a human’s.

Black sun in the spring

Even though most people probably associate black sun with autumn, it also occurs during spring.  Starlings make their way to the salt marshes and perform their dance against the evening sky from the beginning of March until mid-April. This is when they gather strength for the breeding season. Starlings do not only breed in Denmark, they also fly to other Baltic countries and Norway to breed. The breeding season lasts until August, after which the starlings return to the Wadden Sea

to fatten up for winter. The black sun season in autumn stretches over two months, typically from the end of August until the end of October. Afterwards, the majority of starlings migrate to Holland, France and the United Kingdom, where they will winter.

Flying under the influence

Starlings choose the Wadden Sea as a fattening area because of the large cow pastures. The pastures are the ideal habitat for different types of larva, including those of garden chafers and crane flies. These are a favourite food for starlings. However, insect larva are not the only food source of starlings. In late summer and autumn, young starlings in particular enjoy the abundant berries in gardens and hedges at those times of year. However, there is a certain risk connected with the berries. Many of them have been on the ground for a longer period of time and have therefore begun fermenting and forming alcohol. A starling that has eaten berries easily ingests alcohol in amounts that should knock out an animal of its size. However, a starling's alcohol metabolism is twenty-times faster than a human’s, and that's why starlings are still able to manoeuvre with the flock, even when they’re under the influence!


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