Vagrancy (biology)

Irrgast ( sometimes also called exceptional guest ) is primarily a birding technical term.

Among these species are to understand that occasionally appear in areas that are far removed from their actual breeding areas, migration routes and wintering areas. The reasons for such an occurrence events, in particular storms that migrating birds are reported for a long time meteorological, can ship thousands of miles away; However, recent research findings suggest rather that an error occurred in the execution of the genetic migratory.

A generally accepted definition, from which regularity and the number is still to be spoken of vagrants, it does not seem to give. Limiting cases for Germany are for example glaucous gull (Larus hyperboreus ), White-winged Tern ( Chlidonias leucopterus ), Pallid Harrier (Circus macrourus ), red-footed falcon (Falco vespertinus ) and Dotterel (Charadrius morinellus ).

Although vagrants can usually have a certain amount of time in the non- traditional areas survive, but are often unable to return to their actual breeding areas. Report ornithologists the occurrence of vagrants to the competent avifaunistic organizations that verify these reports and publish in successful verification.

Not to be confused with invasion vagrants are birds whose appearance usually associated with population pressure with simultaneous lack of food. Confusion often donate captivity refugees who are considered vagrants.

A study on deciduous singers and chokes

In summer 2007, a team of ornithologists and ecologists from the University of Marburg, the Ornithological Society in Bavaria and the Helmholtz Centre for Environmental Research published - UFZ in the Journal of Ornithology, a study for which they are the thousands of messages of Asian birds from the families warblers and thrushes were evaluated who were lost to Europe. The researchers evaluated their body weight, its wing length, the size of the breeding range, the distance between the breeding and wintering area and the distance between the breeding area and Central Europe for vagrants from 38 species.

They found that the distance between the wintering sites in southern Asia and the breeding grounds in northern Siberia the Distance Siberia - Europe is like. Had been reported, the more vagrants of a particular type from a particular European region, the more precisely corresponded to these distances. Especially often was the Yellow -browed Warbler (Phylloscopus inornatus ) was observed, which has been detected in the years 1836-1991 around a thousand times by volunteer ornithologists in Central Europe as Irrgast. This species breeds south of the Arctic Circle in the Siberian taiga and overwinters in the subtropics and tropics of Southeast Asia. If weather conditions were the cause of vagrants, smaller birds should be blown more frequently than larger ones, so the assumption: The researchers were able to demonstrate by means of statistical analysis no association between the frequency of vagrants and their body size. In addition, the Yellow -browed Warbler kick far too regularly in Europe than that for each observation unusual weather conditions during migration could be held responsible. According to the researchers advised vagrants rather by an error in the execution of their innate migratory program in the wrong wintering area. Existed, the more specimens of species included in their traditional areas of residence, the greater is the likelihood of including some "missing programmed " specimens are located, are flying in the opposite direction instead of towards Asia.

Investigated species that get lost as migratory birds to Central Europe were, in this study, in particular: Balkan Warbler (Phylloscopus orientalis), Dark Warbler (Phylloscopus fuscatus ), Bart Warbler (Phylloscopus schwarzi ), kinglet - warbler (Phylloscopus proregulus ), Yellow -browed Warbler (Phylloscopus inornatus ), Tien Shan Warbler (Phylloscopus humei ), hiking Warbler (Phylloscopus borealis), Crown Warbler (Phylloscopus coronatus ), slate throttle ( Zoothera sibirica ), Erddrossel ( Zoothera Dauma ), Fahl (Turdus pallidus ), White brewing thrush (Turdus obscurus ), Bechstein thrush (Turdus ruficollis ) and Naumann (Turdus naumanni )

Artistic implementation

In her novella Irrgast Mireille Zindel has taken up the subject (using the example of gulls ) as a literary theme.