Cainism
In ornithology, the term cainism denotes the killing of a younger sibling by an older one. The name was given by the Old Testament tradition of Cain's fratricide against Abel .
The use of the term in the ornithological literature is not consistent. Many authors refer to any sibling killing as cainism. In a narrower sense, however, the term is only used for those species in which killing is innate. In order to distinguish the latter types from the rest, the term obligatory cainism is therefore often used.
Emergence
They are killed by pushing them away from the food and / or by direct attacks. The dead young are not usually eaten, but the adult birds often feed them. While in many bird species the killing of nest siblings when there is a lack of food is common, in species with obligatory kainism the act of killing takes place regardless of the feeding situation. Compulsory cainism is therefore innate , similar to the cuckoo's nest clearing behavior, and can also be triggered experimentally by giving the young bird e.g. B. presented a white cloth ball. The attacks of the older sibling on the younger sibling usually begin on the day the latter hatches. The younger bird usually only survives a few days. The adult birds do not hinder these attacks; it has been observed several times that the older young bird continued its attacks even when a parent bird wanted to feed it. The roles of "Cain" and "Abel" are exclusively determined by the order in which they hatch. In experimental conversions of "Abel" to a younger sibling, this "Abel" immediately took over the role of "Cain" and attacked the younger nestling. In further experimental investigations on coffee needles , the aggressiveness of the siblings lasted at least until the large plumage had grown. The clutch of species with compulsory cainism usually consists of two eggs. If both eggs hatch, only the older young will survive, with very rare exceptions.
Occurrence
Cainism is seen in a number of bird species, particularly birds of prey . Compulsory Cainism show, among others Schreiadler ( Aquila pomarina ), Black Eagle ( A. verreauxii ), crown Adler ( Stephanoaetus coronatus ) and the Bartgeier ( Gypaetus barbatus ).
Rescue of the second-born young eagle ( Meyburg method )
The Berlin doctor and spotted eagle researcher Bernd-Ulrich Meyburg is the founder of the spotted eagle reintroduction management. The second young eagle egg is removed from the eyrie, completely incubated outside the eyrie and the second young eagle raised externally (Meyburg method). The aim is to double the number of spotted eagles offspring.
literature
- Valerie Gargett: The Black Eagle. A study . Acorn Books and Russel Friedman Books in association with the Trustees of the John Voelcker Bird Book Fund, Randburg 1990, ISBN 0-620-11915-2 .
Web links
- Cainism in the Lesser Spotted Eagle ( Aquila pomarina ) (PDF file; 385 kB)
Individual evidence
- ^ Reinhard Scheider : Lesser Spotted Eagle Project in Brandenburg: Egg stealing in the eagle's nest . In: our hunt - at home in the area . No. 9-2019 . Deutscher Landwirtschaftsverlag GmbH, Hanover October 21, 2019, p. 7-9 .