A fulldome show about the migrations of birds and their fascinating relationship with the starry night
Every autumn millions of birds across the Northern Hemisphere leave the places where they breed their offspring and fly towards the south in search of warmer places to spend the winter. We still don´t understand all the details of how they find their way in such formidable journeys. We know, though, that they take notice of the duration of daylight and the height of the sun at noon, the Earth´s magnetic field or the memories of the landscapes they flew over in past migrations.
But some of these birds, such as warblers, travel alone and under cover of the night. In the 1950s ornithologists Franz and Eleanor Sauer took some of them into a planetarium to find out if these nocturnal migrants could use the stars for orientation. They saw how vividly the birds reacted to changes in the sky and how they kept pointing to the right direction under the artificial stars of the planetarium. What they found confirmed that, in the first weeks of their lives, warbles were able to create a map of the night sky that they would later use during their yearly migrations.
On the wings of the night is a documentary film for planetariums about the migrations of birds. You will learn about the amazing ideas developed by the ancient greeks about the sudden disappearance of birds from their fields, and also about the mechanisms that birds use to fin the route towards their winter quarters. The show combines spectacular CG animation, starry skies and fulldome video recorded in some of the most beautiful landscapes in the european continent, from the fjords of Norway or the Diepholz swamps in Germany down to the largest wetlands in southern Spain, where migrating birds gather by the millions before crossing the ocean to Africa.
Fundamentally, it all depends on two things: the migratory instinct and the availability of resources. The first, which has been given the scientific name, "Zugunruhe", a German word, compels the birds to travel twice a year. And the matter of resources is not straightforward: in the north there are plenty of resources during the short spring, and only the birds who travel there can benefit from them, while further south, although resources are abundant, there are also more birds to share them, and more types of predators and parasites which may affect the young birds. For this reason many species go north to raise their young and return south in the autumn.
The sedentary species or populations, on the other hand, have achieved a perfect balance between these forces where they live, and over time no longer feel the "Zugunruhe" urge.
What behavioural urges do you think human beings have that are similar to "Zugunruhe"? And any others?
How many migratory birds do you know?
True migratory movements. These are characterized by being voluntary (not imposed by the weather) long distance journeys which are repeated every year on the same dates and which affect all, or almost all of a population.
Local movements. These are carried out by those birds that finish breeding in one location and then move to another location which is safer and has more food; normally, this area is not very far away.
Irruptions and escapes. These occur every now and then in an area where for some reason there is a great abundance of food for one species in particular. They are also triggered as a form of fleeing from a cold wave, a drought or a prolonged rainy period in the birds' usual area.
Dispersal. These movements are made by the young of many species when they leave their parents. They simply fly from here to there looking for new horizons without having a definite direction.
Nomadism. Some species breed every year wherever there is food, sometimes in areas which are very far apart. In other words, they do not have a geographical preference.
Up to what point do migratory birds rely on their instinct to reach their destinations? Well it depends on each species. Let's look at two examples.
From the moment when it stops being fed by its parents at the start of the summer, the melodious warbler must learn to fend for itself. Little by little it travels south, making longer and longer journeys. Until finally it decides to cross the sea from Europe to Africa, travel over part of this content and settle in a location where it will spend the winter. It makes this journey alone, with no help except its instinct and what it learns along the way.
Greylag geese, however, travel in family groups which in turn a part of very close-knit flocks. Thanks to this the young born each year learn from their elders which are the best routes and stopping places on their autumn journey from Scandinavia to central and Southern Spain. Each flock is normally led by an older, highly-experienced female.
Put simply, the chapters of this manual explain:
How to know when it is time to start your journey.
How to navigate by studying the celestial sphere.
How to navigate by studying the position of the sun at sunset.
How to navigate by following the magnetic currents that flow around the planet.
How to navigate using your sense of smell.
How to learn to recognize the approach of bad weather, and landscapes.
How to learn to recognize many different sounds, for example the sound from areas which are richest in food.
Each species has its own manual. However, some manuals do not have all those chapters, while others have many more pages.
Twenty-four centuries ago the Greek philosopher Aristotle had already questioned where the swallows went in the autumn. After realizing that at the beginning of the autumn the birds gathered together over lagoons and marshes, he deduced that they buried themselves in the mud. This belief, with some variations, lasted for just over two centuries. For example, some people argued that the place the birds went to was the moon. The great naturalist Linnaeus, in the XIII century, still believed that the birds hid themselves in holes in houses. Even though in 1555 a Frenchman, Pierre Belon, había propuesto que se iban a África. Pero nadie le tomó en serio.had made the suggestion suggested that they went to Africa. But nobody took him seriously.
Aristotle also explained that when autumn arrived some birds turned into other birds. So, winter robins turned into common redstarts in the spring. This idea lasted in popular culture up until very recently. In many areas of Spain it was believed until very recently that the cuckoo, at the end of the summer, turned into a sparrow hawk.
In order to find a scientific answer they had to have, as always, a hypothesis which could then be tested. The hypothesis with the most supporters was that they were guided by the stars. But how could this be tested? In 1957 Franz and Eleanor Saur placed some migrating birds inside the dome of a planetarium, and demonstrated from the behaviour of the birds that this was the case. But was this innate or learned behaviour?
Ten years later Stephen Emlen also used a planetarium, but this time he installed three different groups of birds under the dome:
- One group reared with views of the real night sky.
- Another group reared inside, with no view of the sky.
- A third group reared under a false sky, where the stars rotated around Betelgeuse, rather than around Polaris.
When the autumn migratory season arrived, the first group oriented themselves within their cages away from Polaris. In other words, towards the south, the route that their species had always followed on this date. The second group were unable to orientate themselves in any direction at all. They felt the migratory instinct, but they did not know where to go. What the third group did was to orientate themselves away from Betelgeuse, the star that they had learned to use as a reference. In this way Emlen proved that young birds in the northern hemisphere learn to orientate themselves from north to south from the rotational pattern of the terrestrial sphere.
These are some of the voices of travelling birds from our countryside. Try to match each voice with the bird
Nowadays GPS technology allows us to track the migrations of birds and draw their routes on a map. Here are some examples worth watching.
Arctic terns are marine birds that eat small fish. Some of their European populations fly towards the centre of the Atlantic Ocean before continuing on towards South Africa, rounding the Cape of Good Hope and continuing over the Indian Ocean until arriving in the south of New Zealand. Once there, they go on to the Antarctic coasts and return again in the spring.
Bar-tailed godwits are wading birds the size of a pigeon that feed in areas of mud using their long beaks to search for invertebrates. A few years ago it was shown that the godwits that breed in Alaska travel in one go to New Zealand to spend the winter. To do this they cross almost diagonally the largest ocean area of the solar system for nine days and nights, without stopping until arriving at their favourite marshland. A record of nearly 11,500 km.
From the end of the spring these birds with their sharp-edged silhouette arrive in all European and Asian cities. They arrive just in time to raise their families, nesting in holes in our buildings and to leave at the end of the summer. Their destination is Africa. Even, common swifts in Beijing fly there. But that's not all: from the time they leave until the time they return, they do not land on the ground for months. They spend all these months on the wing.
Birds are not the only migratory animals. We need look no further than man; many cultures of humankind throughout history have adopted a way of life that took them to cold areas in the summer and warm ones in the winter. The larva of crabs and some copepods only 1-2 millimetres in length migrate through the sea water just like the huge blue whales of up to 27 metres in length or eels and salmon. The American monarch butterfly each autumn travels an average of 4,750 km between North America and Mexico. Canadian caribou come and go on the tundra just like the African wildebeest and zebras do in the Savannah.
What's more: birds are not the only animals that use the stars to guide them. Science has discovered, for example, that sealsuse the stars to find their return route to the coast from far out at sea. And some dung beetles do the same to navigate through the desert.
Migration is a very demanding challenge. Sometimes a very high percentage of young birds each autumn lose their lives due to a lack of experience; they might be picked up in a storm that takes them out to sea, they may not have eaten enough before attempting to cross the Sahara or they may not have recognized a predator's silhouette in time. These are all natural threats. They form part of the risk taken by each species in travelling to find different resources in remote destinations. Their populations have been facing these threats for millennia.
However, there are other threats, many of them very recent, that the birds are not equipped to tackle. Yes, you've got it: these threats are caused by various human activities, and they are already causing very serious conservation problems. These are some of them:
- Mass hunting. .
This is still practised in many places in the Mediterranean, either by shooting or using traps of different kinds, such as the so-called “Parany” in the Spanish region of Levante. A century ago the North American passenger pigeon, which was abundant, disappeared for ever for precisely this reason.
- Destruction and contamination of their resting and feeding areas..
- Climate change, which alters the cycles of the seasons.
There are countless musical compositions inspired by birdsong in all cultures and throughout history. In the western world what we call today "classical music" includes works created by such immortal composers as Vivaldi, Beethoven, Schubert, Brahms, Messiaen... You would definitely recognize many of these works from just the first few notes.
Many of them include passages that evoke spring by using the song of migratory birds, often reproduced by wind instruments. An example of this is the cuckoo and the quail. And, above all, the nightingale ), because the voice of this bird is the most beautiful of all the songs heard in the European countryside.
Modern music has also found inspiration from birds. In one Pink Floyd track, for example, a lark can be heard in the background. And who hasn't sung along to A hundred seagulls where will they go.
According to Greek mythology, it was Hermes, messenger of the Gods, who invented the cuneiform alphabet by copying the V-shaped formations of the cranes flying overhead. And Hermes' emblem, of course, was a crane
Literature throughout the world is full of references to the journeys of birds. Here is a Japanese haiku from the XVIII century written by Yosa Buson:
The geese have gone
and the rice field before the house
seems far away
Try reading it aloud to see how it sounds in Japanese:
kari yukite kadota no toku
The protagonist of one of the most famous children's books ever is a child called Nils Holgerson who travels with a flock of geese on their journey from the south to the North of Sweden, and back. It was written over a century ago by the Nobel Prize winning author Selma Lagerlöf with the title "The Wonderful Adventures of Nils" and it is still in print in almost every language.
If you would like to enjoy these awesome journeys first hand, not far from where you live, there will definitely be one or several places which are interesting at certain times of the year. It might be that the birds gather there to rest or to feed during their migration. In these places, flocks of different species also pass through in the autumn or the spring. Or they may be overwintering areas for species coming down from the north. Remember to take your binoculars with you and a bird identification guide.
The best thing to do is to get in touch with a group of bird watchers in your town, city, area or county. They will give you good advice and may even invite you to join in their activities.
There are also several places which are exceptional because of the quantity of birds of different species that can be seen passing through, sometimes an endless stream of them. In Spain, this happens over the strait of Gibraltar, which is internationally famous. Also, in the Pyrenees, at the pass of Organbidexka. The best place to watch sea birds on migration is the cape of Estaca de Bares in Galicia.
Particularly outstanding places in Europe are the south of Sweden, (Falsterbo) and the north of Denmark (Skagen), the French capes of the English Channel (cap Gris-Nez) and several British and Irish capes. Further east, in the Bosphorus strait (in Istanbul) and the area of Batumi, in Georgia. Try and find out about where these places are and which birds pass through each one.
The images On the Wings of the Night are the result of different techniques, such as 3D animation, timelapse, fulldome video and many other surprises