Irrgast
Irrgast (sometimes also called exceptional guest ) is primarily an ornithological technical term.
This includes species that occasionally appear in areas that are far from their actual breeding areas , migration routes and wintering areas. Meteorological events have long been identified as reasons for such an occurrence, in particular storms that can transport migrating birds over thousands of kilometers; However, more recent research suggests an error in the sequence of the genetically anchored migration program.
There does not seem to be a generally applicable definition of the regularity and number up to which wanderers should be spoken of. Borderline cases for Germany are z. B. Ice gull ( Larus hyperboreus ), white-winged tern ( Chlidonias leucopterus ), steppe harrier ( Circus macrourus ), red-footed falcon ( Falco vespertinus ) and black-bellied plover ( Charadrius morinellus ).
Odd guests can usually survive in the non-ancestral areas for a certain period of time, but are often unable to return to their actual breeding areas. Ornithologists report the occurrence of wanderers to the responsible avifaunistic organizations, which check these reports and publish them if verification is successful.
Irregular guests are not to be confused with invasive birds , the occurrence of which is mostly related to population pressure and a simultaneous lack of food. Confusion is often caused by prison refugees who are mistaken for wanderers.
A study on warblers and thrushes
In the summer of 2007, a team of ornithologists and ecologists from the Philipps University of Marburg , the Ornithological Society in Bavaria and the Helmholtz Center for Environmental Research - UFZ published a study in the Journal of Ornithology for which they used several thousand reports from Asian birds from the families of the Had evaluated leaf warblers and thrushes that had strayed to Europe. For stray visitors from 38 species, the researchers evaluated their body weight, their wing length, the size of the breeding area, the distance between the breeding and wintering area and the distance between the breeding area and Central Europe.
They found that the distance between the wintering quarters in southern Asia and the breeding grounds in northern Siberia is the same as the distance between Siberia and Europe. The more wanderers of a certain species were reported from a certain European area, the more exactly these distances corresponded. The yellow-browed warbler ( Phylloscopus inornatus ) was observed particularly frequently, which had been reported as an irregular visitor around a thousand times by volunteer ornithologists in Central Europe between 1836 and 1991. This species breeds in the Siberian taiga south of the Arctic Circle and flies to the subtropics and tropics of Southeast Asia to hibernate. If weather influences were the cause of wanderers, smaller birds would have to be blown away more often than larger ones, so the assumption: With the help of statistical analyzes, however, the researchers could not prove a connection between the frequency of wanderers and their body size. In addition, the yellow-browed warbler appears far too regularly in Europe for unusual weather conditions on the migration route to be responsible for any observation. According to the researchers, stray visitors rather end up in the wrong wintering area due to a mistake in their innate migration program. The more specimens of a species existed in their traditional habitat, the greater the likelihood that some “incorrectly programmed” specimens would also be found that were flying in the opposite direction instead of going to Asia.
Investigated species that get lost as migratory birds to Central Europe were, in this study in particular: Eastern Bonelli's Warbler ( Phylloscopus orientalis ), Dusky Warbler ( Phylloscopus fuscatus ), Bart Warbler ( Phylloscopus schwarzi ), Firecrest-warbler ( Phylloscopus proregulus ), Yellow-browed Warbler ( Phylloscopus inornatus ) , Tienschan-Laubsänger ( phylloscopus humei ), Arctic Warbler ( Phylloscopus borealis ), crown Laubsänger ( Phylloscopus coronatus ), slate throttle ( Zoothera sibirica ), Scaly thrush ( Zoothera dauma ) Pale throttle ( Turdus pallidus ), White brewing throttle ( Turdus obscurus ), Bechstein throttle ( Turdus ruficollis ) and Nauman's thrush ( Turdus naumanni )
Artistic implementation
In her novella Irrgast , Mireille Zindel took up the motif ( using the example of seagulls) as the main literary theme.
See also
literature
- Ralf Wassmann: Ornithological pocket dictionary. Explanation of technical terms, with an English dictionary. Aula-Verlag, Wiesbaden 1999, ISBN 3-89104-627-8 .
Individual evidence
- ^ Robert Pfeifer, Jutta Stadler, Roland Brandl: Birds from the Far East in Central Europe: a test of the reverse migration hypothesis. Journal of Ornithology Volume 148 (Issue 3), 2007, pp. 379-385, doi : 10.1007 / s10336-007-0140-6
- ↑ Mireille Zindel: Irrgast. Salis-Verlag, Zurich 2008, ISBN 978-3-905801-07-1 .