Flying off course(the Handbuch der Vögel Mitteleuropas (ha...)

Date:4/10/2008

the Handbuch der Vögel Mitteleuropas (handbook of birds of Central Europe) from the start of ornithological records to the early 1990s. Eight species from the leaf-warbler family and six from the thrush family caught the scientists' attention as vagrants. One species that was spotted particularly often was the Yellow-browed Warbler (Phylloscopus inornatus), which was reported by voluntary ornithologists in Central Europe around a thousand times between 1836 and 1991. This species breeds in the Siberian taiga south of the Arctic Circle and overwinters in the subtropics and tropics of South-East Asia. The other Asian leaf-warbler species were observed much less frequently, if at all, in Central Europe. By contrast, five thrush species were reported nearly 100 times. If vagrants were brought by the weather, smaller birds should be blown off course more frequently than larger ones. However, using statistical analyses, the researchers were unable to find any correlation between the frequency of vagrants and their body size. In addition, the Yellow-browed Warbler occurs far too regularly for every sighting in Central Europe to be explained by 'unusual' weather conditions during migration.

The species most likely to land in Europe are the ones that are widespread in Asia and are as common there as their relatives the chiffchaff and European willow warbler are in Central Europe. "The more numerous a species is, the greater the probability that one of them will be 'wrongly programmed' and go astray," explains Dr Jutta Stadler of the Helmholtz Centre for Environmental Research (UFZ) in Halle/Saale. "They fly the same distance but in the opposite direction, which takes them to Europe. This is why we have relatively large numbers of vagrants from Asia here."

Wrong way down the migration flyway

The scientists suspect the cause is an error in the genetic migratory programme. The flight direction and flight duration are passed on from one generation to t
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Contact: Tilo Arnhold presse@ufz.de 49-341-235-1635 Helmholtz Association of German Research Centres Source:Eurekalert

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