Humans have always been fascinated by bird migration. For a long time, there were only wild speculations and unquestioned stories trying to explain this spectacle. Even Aristotle, the founding figure of all critical scientific observation, thought that Redstarts turned into Robins when they left during winter.
In the 18th century, the biologist Linné still thought that Swallows would spend the winter like frogs on the bottom of lakes and ponds. At the same time he was the first to study bird migration (migrationes avium) by observing and registering migratory birds. This way he could find out their exact chronological movements. For a long time, this and other direct observations were the only methods of researching bird migration. .
Bird ringing for scientific purposes has advanced bird research. Hans Mortensen, a Danish teacher was the first to ring birds. Around 1890 he ringed birds and inscribed the bands with his name and address in the hope they would be returned to him if found. This way he got reliable information about where birds come from and where they go.
During the past 100 years the methods of catching and ringing birds have changed a lot and do less harm to the birds than in prior times. Since 1890, about 55 to 60 million birds have been ringed around the world and the findings are priceless. There is a strong network of cooperation, coordination and harmonization of scientists around the world that guarantees the success of ringing birds.
Bird migration was not caused by a single factor. It is the result of the interaction of several factors: Food is not always available in the same necessary amount. But at places, where there is high abundance of food birds can not stay during winter. Birds may face more risks wintering in Europe than migrating to east Africa. They take advantage of their ability to fly to follow geographic and seasonal fluctuations of biomass-production. They simply go where living conditions are acceptable. On the global scale biomass-production varies geographically and seasonally. Migration enables birds to go wherever biomass-production is high.
Migrating birds are divided into three groups:
1. Migrating birds of the Neusiedler See region breed here in summer, but leave the breeding area every year and migrate to warmer countries. (summer birds)
2. There are migratory birds that rest in the Seewinkel area to restore energy or to moult. They can only be found in the National Park during migration time. (mainly spring and autumn)
3. There are birds that do not breed here but spend the winter here or stay for some time before going to their winter destinations.
There are three main flyways in the Old World:
- The East-Atlantic flyway, where birds from Europe, Siberia, Greenland and east Canada meet to winter along Europe’s and Africa’s west coast. To cross the Mediterranean, these birds use the shortest way via the Bosporus coming from eastern breeding areas and via Gibraltar if coming from Western Europe. Both ways cross the Neusiedler See region.
- The central Asian flyway extends from central Asia to the Indian subcontinent; going around the Himalaya.
- The eastern Asian- Indo-pacific flyway leads from north-eastern Siberia to Australia.
Migration strategies, invasions, dispersal
Depending on the distance, bird migration is separated into long-distance, medium-distance and short-distance migration of which the most impressive is the long-distance migration. All European birds that winter south of the Sahara are among long-distance migrating birds. Their migration routes are a minimum of 3,000 km long but generally they are much longer.
The Curlew Sandpiper from north Siberia the winter in South-Africa migrates more than 12,000km.
Migration of Curlew Sandpiper
Even small birds, like the Marsh Warbler fly up to 10,000km in one direction.
Migration of Marsh Warbler
Medium-distance migrants are all birds that migrate from Europe to North-Africa (1.000km), like the Kentish Plover.
Short-distance migrants like the Skylark, move from breeding grounds in Central Europe to Western Europe or Italy where winters are mild.
Within a species not all populations may be migratory. There can be short, medium and long distance migrants. Buzzards in Central Europe migrate only short distances or do not move at all. While Buzzards in north Scandinavia or Russia winter in east and South-Africa.
Regular seasonal journeys between the breeding and wintering area are the most common migration movements. Additionally, there are other types of migration. The Waxwing, for example, inhabits coniferous woodland in the north and is a well-known ”invasion bird”. In some years huge flocks can be found far from their usual wintering areas.
If food supplies (rowan berries) get short after a cold summer, parts of the population move to the south or south-east. The invasion is unpredictable and sudden and was seen as a warning against war, plagues or inflation in the past. Invasions can occur several years or decades apart.
Many Nordic water birds like the Goldeneye move to winter areas that are as close as possible to their breeding grounds. They always stay just south of the snow and frost line, like the ice-free waters of Central Europe. In case of a cold-snap, they move a bit southward. On the other hand, if temperatures are mild, they move northward.
Many young birds migrate outside the usual migration time and route: Young Sedge Warblers, for example, leave their birth place and move around. They seem to look for potential breeding sites. Only after this movement, that can include hundreds of kilometres, they start their actual autumn-migration.
When does bird-migration in the Neusiedler See region take place?
Migration takes place the whole year around.
In the beginning of February, Starlings, Skylarks and Lapwings are the first birds that arrive in the area.
In the beginning of May, Bee-eaters from South-Africa and Red-breasted Flycatchers from South-Eastern Asia are the last to arrive in Seewinkel.
In August, Storks, Swifts and Rollers start to migrate south. If temperatures are mild, Greylag Geese stay until December, before migrating to Southern Europe.
Birds have two ways of finding their way during migration: via compass or navigation.
When using the compass, the bird keeps a constant angle to the sun or the magnetic field of the earth. That way, the bird flies in the right direction, but does not know how long the journey will be. By navigating, the bird finds the right destination, like its breeding or wintering area that it already knows.
The earth is a huge magnet with a north and a south pole that are close to the geographic poles. Birds use the earth’s magnetic field for orientation but can also navigate by using the position of the sunset, infrasound and olfactory cues.
Birds can lay down enormous fat reserves, which enable them to fly long distances. During preparation birds gain about 35-90% of their weight, so the body fat rises up to 10-15% of the total weight.
It is important to fly as energy-efficiently as possible. Bird populations from the north that have to fly longer distances usually have large broad wings. Storks, pelicans or birds of prey rely on thermals rising from the ground to gain altitude.
Although bird migration has been studied for thousands of years, scientific research is quite young. Chronological and spatial researches were made. A network of researchers in Great Britain, Hungary, Switzerland and the USA formed. In 1889, H. D. Mortensen from Denmark was the first to ring birds.
Apart from this traditional method of using metal rings, plastic rings and collars of different colours are in use. Radio-telemetry has become more and more common during the past years.
Protection of the migration routes
If birds migrate across several countries to winter in a distant country, protection has to be inter-regional. There should be resting areas and roosts wherever birds pass by.
But most of the international agreements are no more than supporting measures, like embargos or protection requirements. The RAMSAR-Convention (1971), whereby states agreed to preserve resting and nesting areas for water birds is a huge success for international nature conservancy efforts. The Neusiedler See region was the first and largest area to become RAMSAR region in Austria.