Black Sun - a nature phenomenon in the Wadden Sea

Torben Kjærgaard Andersen, Vadehavscentret & Inger Sønnichsen, Naturcentret Tønnisgård

The gIANT pANTry

Translation: Nanna Mercer, Sirius Translationpage 1 of 4

Black sun occurs when, at the sunset, large flocks of starlings congregate on specific loca-lities to settle down in the reed forests. A large flock of starlings can almost darken the setting sun as they dance in the evening sky - hence the name, black sun.

It is not unusual for starlings to congregate in large flocks of several hundred thousand individuals and when they start to dance in the evening sky, their flight formation can make you think of a ballet perfor-mance. However, the situation is quite different for the starlings. Their dance is a defense mechanism against attacking birds-of prey in the same manner as that seen in schools of fish. By assembling in huge flocks, the birds, as one entity, there are many eyes to detect potential danger, while at the same time their flock formation is confusing for an attack-ing predator. It is typically the fast and maneuvera-ble sparrow hawk that attacks the starlings, but the merlin, the blue hawk, the marsh harrier and the go-shawk are also on the prowl. In a few cases, the wor-ld’s fastest animal, the peregrine falcon, may also interfere in the fight to get starling on the evening menu. So -the starlings do not gather in flocks to de-light their audience with a dance performance on the evening sky, but to avoid being eaten, still, why not enjoy the beautiful sight.

Why stay overnight in the reed forests?Reed forests can be found in the wetlands throug-hout the marsh, where neither the fox nor any other predator will venture into the deep mud and water to reach their goal, the starlings. Birds-of-prey are not active during the night since they use their sight when they hunt for prey. The starlings are therefore dry and relatively safe in the reed forests during the night, or until the sun rises and the starlings wake up.

Ballet in the evening sky – no collisionsBy itself, the starlings’ dance can evoke great enthu-siasm in their audience, often followed by a feeling of wonder at the starlings’ ability to move in the sky at

The starlings dance is a defense mechanism against attacking birds-of prey.

BLACK SUNA UNIQUe NATUre pheNOMeNON IN The WADDeN SeA

AUTUMN WINTERSUMMERSPRING

ExpEriEncE Black sun in ..


The gIANT pANTry


such lightening speed as one entity, but without col-liding. Do the starlings have some mutually agreed upon traffic rules that allow then to avoid collision in the middle of this chaos of birds? The answer is no - the starlings are actually able to steer clear of each other strictly by reason of their lightening fast reactivity. A starling is ca. 20 times faster than man.

Black sun - both spring and autumnAlthough most people associate black sun with the autumn, this phenomenon, also known as murmura-tion, occurs in the spring as well. For about 3 to 4 weeks from the middle of March to the middle of April, the starlings visit the marshland, and perform their dance in the evening sky. They are gathering strength for their most important task, that of having young. The starlings breed not only in Denmark, but also migrate to the countries around the Baltic Sea as well as to Norway. The breeding season lasts until August, where the starlings return to the Wad-den Sea area to gather strength for the winter. The black sun season typically stretches over more than 2 month, from the end of August until the end of Oc-tober, after which most of the starlings migrate to Holland, France and Great Britain, where the over-winter.

Before it was known that the starlings migrated south for the winter, it was thought that they actually

overwintered on the bottom of lakes and bogs. For why else could they suddenly show up at exactly the same locality each spring? Since then we have be-come more knowledgeable about the habits of star-lings and other birds. A great deal of the knowledge

Although most people associate black sun with the autumn, this phenomenon occurs in the spring as well.

In the starlings’ nests large numbers of mites and other parasites can be found. In a mite infested nest, the young can lose up to 10 percent of their blood per day, which gives a much poorer chance of survival. To keep the mites down, the male lines the nest with poisonous plants, such as wormwood and cowslip that contain natural remedies against plant eaters. A male starling courting a female will be judged on his ability as a phar-macist, and if the nest’s content of poisonous plants is not to her taste, his will be ignored.

ThE young is safEguardEd using chEmical warfarE

At nightfall, when the starlings settle down in the reed forests, there is competition for the best sleeping per-ches, which are those around the middle of the reeds. Starlings perching too high are more exposed to the wind and the weather, while those perching too low are in danger of being hit by droppings from those higher up. So, there is often a hustle and bustle before sleep-ing perches have been allocated and the night is quiet in the reed forest.

compETiTion for ThE BEsT slEEping pErchEs


The gIANT pANTry


concerning birds’ migrating pattern is thanks to the Danish school master Hans Chr. C. Mortensen. He was the first person to have success with ringing birds, for in this way to follow their migrating pat-terns. The birds were ringed with a numbered mar-ker and if birds ringed in Denmark were later obser-ved in another locality, it was possible by repeated observations to get an idea of the migration pattern of specific bird populations.

The Wadden Sea area - the starlings’ preferred restaurantThe starlings’ choice of the Wadden Sea area as the locality for fattening up is predicated on the large areas with pastures for grazing cattle that are still found in these parts. The pastures represent the ideal habitats for the starlings’ preferred food: larvae from garden chafers and crane flies. Insect larvae, however, are not the only source of food, for espe-cially in the late summer and the early autumn, the young starlings profit by the large number of ber-ries found in gardens and hedges this time of year. Consumption of this food source is connected with certain ”security” risks, for many of the berries have lain on the ground for some time and have there-fore started to ferment. During fermentation, the sugars in the berries are broken down and become

energy, CO2 and alcohol. The berry-eating starlings are thus consuming rather large quantities of alcohol - enough to more or less anaesthetize most other animals the same size. The starling has an alcohol metabolism that is 15 times greater than mans and so, their alcohol consumption does not present a se-curity risk for either their health or the air traffic.

The best singer in the gardenAside from its abilities as an aerial acrobat, the star-ling is also known as a talented song bird. It is pre-dominantly the male that sings and, in the spring, his primary mission is to attract a female to his nest. The greater his song-repertoire, the better his chance of success. The male starling is delightfully creative when the repertoire needs enlarging and finds inspi-ration in his immediate surroundings. Male starlings have been observed to imitate the ring tones of a mobile phone, the meowing of a cat and a squeaky door. At a soccer stadium, a starling even imitated the sound from the referee’s whistle. Reputedly it caused a bit of confusion at several local soccer matches when the starling’s referee-whistle song rose pari passu with the increase in the real referee’s whistle activity - likely because the referee whistle in the eyes of the starling was seen as the song from a competing male.

Aside from its abilities as an aerial acrobat, the starling is also known as a talented song bird.


The gIANT pANTry


Black sun can be experienced in the wetland areas containing reed forests around Ribe and Tøndermarsken.

Vadehavscentret arranges tours in the Ribe area, and in Tøndermarsken, Sort Safari is the organi-zer

Things To do

VadehavscentretOkholmvej 5 Vester Vedsted DK-6760 RibeT: +45 75 44 61 61E: [email protected] W: www.vadehavscentret.dkNaturcentret TønnisgårdHavnebyvej 30 DK-6792 Rømø

T: +45 74 75 52 57E: [email protected] W: www.tonnisgaard.dk

lEarn morE aBouT Black sun hErE ...

Millions of starlings overwinter in Rome, where they cause problems for the city’s inhabitants. Cars, bicy-cles, not to mention the good citizens in Rome, are ex-posed to real air bombing of droppings from the many starlings. Most of the locals are prepared and have an umbrella or a newspaper to hand, but the problem has become so great that some of the municipalities have hired ”starling hawkers” to scare the birds away from the more affected areas. By playing the starling’s war-ning screams using powerful amplifiers the problem (the starlings) is moved to another and hopefully less affected locality.

Black sun in romE

Vadehavets Formidlerforum is a partnership of visitor centers that mediate the Wadden Sea’s natural and cultural heritage. VFF’s main activity is to coordinate projects that highlight the nature and culture heritage of the Wadden Sea..Learn more at www.vadehav.dk

aBouT VadEhaVETs formidlErforum...

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Black Sun - a nature phenomenon in the Wadden Sea