The Winter-Stork - A Phenonenon of Modern Times
Friday, May 02 2014 @ 07:00 PM EDT
Contributed by: Gabi
More and more of White Storks are staying at their nests in Europe during the winter instead of migrating to the south, and many people are worried whether this migratory bird at all can overwinter at our degree of latitude.
LBV/Bavaria (Landesbund fuer Vogelschutz - the bird and nature conservation union) says it would work. Only after weeks of severe cold and a thick blanket of snow would food be scarce. These so-called winter storks move around about 30 kilometers (about 20 miles) to find food, particularly mice, snails and fish.
Traditionally the White storks migrated to the south each year in autumn to warmer areas. Until the previous 20 years almost 80% of all White Storks have been migrators of the eastern route (shown in pink on the right side of the map below). That means that they flew over Turkey, Syria, Israel and Egypt to East and South Africa, a distance of about 10,000 km (6,200 mi).
But the number of the migrators of the western route (the pink routes on the left side of the map) has been increasing from year to year. These migrators fly over France, Spain, and Gibraltar to North Africa, and then to parts of West Africa like Morocco, Senegal and the Niger-Delta. The reason why storks are more frequently taking the western route to Spain is that they can find nourishing food from garbage dumps and a new species of crab in the region after flying only a few hundred kilometers.
For a few, the shortest route would take them over the Mediterranean Sea to Tunisia and West Africa (the green routes in the middle). White Storks rely on the uplift from air thermals to soar and glide the long distances of their annual migrations between Europe and Africa. However, since air thermals do not form over water, they generally detour over land to avoid the trans-Mediterranean flights that would require prolonged energetic wing flapping. Thus, flocks spiral upwards on rising warm air until they emerge at the top, up to 4,000m-4,500m above the ground. Then up to a height of 4,000m (13,000 feet) they can glide with a speed of 100 km/h (62 mph). They fly about 150-300 km per day while migrating.
The number of white storks which do not fly to the south anymore is increasing from year to year. One of the sub-categories of the so-called "Winter-Storks" are those which don't migrate but occasionally take a "winter-escape." That means that these storks fly in autumn away from the breeding range, not to Spain but only a few hundred kilometers to the Elsass area on the border between Germany and France. This region has a milder climate than the eastern regions of Germany. In Elsass they fly to semi-open aviaries where they can get food; such feedings are strictly prohibited in Germany. If during a mostly mild winter in Germany a few frosty days occur with heavy snowfalls, the storks can fly within a few hours to the warmer Elsass so there is no need to feed them.
But there are also a few exceptions. Winter-storks like our stork couple Anna von Steinfeld & Gerome de Vias who have lived for the last 5 years in Hoechstadt do not leave their area and habitat. During a severe winter they wouldn't find enough food and they would starve, so they get supplementary feeding, which requires special permission from the government. The same supplementary feeding option is available for the stork couple Romeo & Julia from the Isny nest.
Reasons for such a high number of Winter-storks and Winter-escape–storks are global warming and possibly the mixing of the population of white storks with the special breeding storks from Switzerland and Baden-Wuerttemberg. The special breeding storks are the result of programs in the seventies and eighties to increase the population of stork species which were endangered at that time.
This genetic mixing destroys the genetically inherited sense of direction and the magnetic sense that enables the storks to use the Earth's magnetic field. The White Stork is no longer on IUCN - The Red List Of The Threatened Species - and breeding stations like that were never allowed in Bavaria.
It is encouraging that all young storklets still migrate, but now they mostly go only to Spain, and then they return to start breeding when they are only one year old - and have little success because they are too young. Traditionally storklets have stayed at their migration range for at least 2 years.
The phenomenon of the Winter-Stork is an open-ended experiment of nature and may not be disturbed by feeding of the storks. The highest priority of our nature conservation act is to protect all the wild living species, and part of that is preventing human beings from intruding into nature.
Many thanks to Oda Wieding, stork expert and biologist of LBV (Landesbund für Vogelschutz in Bayern) and to Judy Barrows, my language assistant, for their help and support.
Hoechstadt storks at their nest in winter (top of page) courtesy of cococat9
Romeo and Juliet from the Isny nest looking for food courtesy of Ulli - Isny