This news release is available in German.
If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to make restaurant owners pay up. Similarly, mafia-like behaviour is observed in parasitic birds, which lay their eggs in other birds' nests. If the host birds throw the cuckoo's egg out, the brood parasites take their revenge by destroying the entire nest. Consequently, it is beneficial for hosts to be capable of learning and to cooperate. Previously seen only in field observations, scientists at the Max Planck Institute for Evolutionary Biology in Pln have now modelled this behaviour mathematically to confirm it as an effective strategy.
Some parasitic birds, such as the North American brown-headed cowbird (Molothrus ater), are observed to punish host birds by destroying their clutches if their eggs are rejected. Consequently, the hosts accept a certain degree of parasitism as long as they can raise their own offspring alongside the parasitic chicks. "We tested and confirmed the mafia hypothesis, which was controversial among scientists," explains Maria Abou Chakra, lead author of the study. The parasitic birds use their behaviour to extort the hosts, forcing them to cooperate. "They give the hosts no choice. If they wish to avoid retaliation, they need to keep the foreign egg."
For the theory to work, two points are absolutely crucial: the host birds must be capable of learning, and the parasites must approach the same nests more than once. Only then does the mafia-like behaviour have the desired effect. "For the hosts, the best thing is to remove the foreign egg from their own nests. But if they encounter a ret
|Contact: Dr. Maria Abou Chakra|