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The term Überspringzug or Überrollzug (engl. " Leapfrog migration " of leapfrog = Leapfrog) referred to in the ornithology a particular Zugmuster within a species It draws a - mostly northern breeding -. Population about - mostly southerly - breeding or wintering area a or past another population to hibernate in more distant areas. The birds of the “skipped” population do not migrate that far, they are mostly resident birds , short-range or partial migrants .
Most likely, such a migration pattern arises from the fact that a species expands its range to the north. Due to the prevailing climatic conditions there, the northern populations are forced to migrate to warmer areas in winter. They also cross the area of the original population, but cannot overwinter here because the birds that live there act as food competitors and, with their knowledge of the local conditions, have an advantage. It is therefore advantageous for both populations if the migrating part moves to other regions, even if this results in a longer migration route. The population that overwinters in their breeding areas (or only migrates short distances) can start the breeding business quite early, the migrating population can persist in the wintering areas until the conditions for a retreat are given.
An example of such migratory behavior is the North American fox bunting ( Passerella iliaca ), which occurs along the west coast from Mexico to Alaska and which has probably spread from the south. The northern subspecies unalaschcensis , which breeds on the Alëuten , overwinters in California . This is much further south than the range of the subspecies townsendi , which breeds on the west coast of Canada and winters in the northwestern United States .
Similar migration patterns have also been found in Eurasian species such as the song thrush or the ringed plover.
The term “leapfrog migration” should not be confused with the so-called “ leap frogging ” , which can be observed as courtship behavior in some bird species.
literature
- J. Elphick: The Atlas of Bird Migration , Marshall Editions, Cape Town 2007, ISBN 978-177007-499-6
- I. Newton: Speciation And Biogeography Of Birds , Academic Press, London / San Diego 2003, ISBN 0-12-517375-X
Individual evidence
- ^ UN Glutz von Blotzheim, KM Bauer: Handbook of the birds of Central Europe (HBV). Volume 11 / II, Passeriformes (2nd part): Real thrushes: Turdidae, AULA-Verlag, ISBN 3-923527-00-4 , p. 1070
- ^ Newton, p. 526f, s. literature