Train unrest
Zug unrest is a technical term from ornithology and experimental behavioral biology . It describes the increased motor activity of migratory birds in the days immediately before the start of their bird migration , i.e. before the start of departure for their summer roosts (in spring) or winter roosts (in autumn). The unrest among night migrants is particularly noticeable: "While members of this large group of birds normally rest at night outside of the migration period, they are active during migration times at night, sometimes all night." Are migratory birds kept in so-called registration cages and thus prevented from migrating , the unrest in the train can be recorded quantitatively if, for example, movable perches are used which are mounted on microswitches and whose movements are recorded electronically.
The migratory unrest lasts as long as the bird would migrate in the wild: The investigation of more than 100 species showed that "the migratory unrest is a regular expression of the migratory behavior of free-living conspecifics and provides information about the migration process in the wild." After the migration has ended, birds kept in cages also return to their extraordinary day-night rhythm .
In Germany, for example, Wolfgang Wiltschko has been researching the magnetic sense of migratory birds since the mid-1960s and developed devices that are able to precisely register the cardinal points to which his test animals tried to fly. In addition to the direction, the frequency of movements could also be registered in his equipment. It has also been shown that birds that are completely isolated from their natural environment become more motorically active at exactly the time when their free-living conspecifics move away.
Also Eberhard Gwinner and Peter Berthold shown by the example of hand-reared in the laboratory birds after that the seasonal migration due to internal - hormonal initiated changes in state and not in response to changes in the environment -.
literature
- Barbara Helm, Theunis Piersma and Henk van der Jeugd: Sociable schedules: interplay between avian seasonal and social behavior. Review in: Animal Behavior. Volume 72, No. 2, 2006, pp. 245-262, doi: 10.1016 / j.anbehav.2005.12.007