Intergradation

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Under intergradation mixing is two or understood several subspecies of a species in a regional area. One example is the intergradation of the two subspecies of the carrion crow ( Corvus corone ), which takes place along a line from Schleswig-Holstein via eastern Germany to eastern Austria . The Elbe forms this line in the area of ​​Schleswig-Holstein and East Germany . East thereof incubates the Nebelkrähe ( C. c. Cornix ), west of the line, the pure black Rabenkrähe ( C. c. Corone ). The intergradation zone , also known as the contact zone , in which the two subspecies mix, is between 40 and 150 km wide. In the appearance of the offspring, the characteristics of the parents appear in stepless variation. Another, even longer contact zone exists in North America between the members of the auratus group and those of the cafer group of the golden woodpecker . It stretches from southern Alaska to Texas.

literature

  • E. Bezzel / R. Prinzinger: Ornithology. Ulm-Stuttgart. 2nd edition 1990. ISBN 3-8001-2597-8