Cuckoos mimic hawks to scare hosts
Sun, 17 Apr 2011 16:28:14 GMT
A recent study has revealed that cuckoos which have hawk-like appearance scare the birds whose nests they invade and lay their eggs undisturbed.
According to the report published in the journal Behavioral Ecology, the parasitic birds have evolved plumage patterns that have made them look like hawks and have the ability to scare host species.
Cuckoos are brood parasites who lay an egg in another bird's nest and leave the host to raise their chick. To be successful in doing so, however, they have to lay the egg without being "mobbed" or attacked by the nest's owner.
"We noticed in another experiment that great tits and blue tits were just as afraid of cuckoos as they were of sparrow hawks," explained Dr. Justin Welbergen, leader of the study from the University of Cambridge, UK.
As cuckoos are not a threat to host species, scientists wondered if it was the hawk-like appearance which frightened them, the state-funded BBC reported.
Welbergen and his team placed stuffed dummies of cuckoos and sparrow hawks near the nests of reed warbler, a cuckoo host species which were found to be scared of cuckoos.
"The most striking similarity between a cuckoo and a sparrow hawk is the bar patterns on [both species'] underbellies," Dr. Welbergen explained.
The bellies of the cuckoo and sparrow hawk models were therefore covered with white cloth, to study the reed warbler's reactions to both the covered and uncovered models.
"We found that the reed warblers were more reluctant to approach the birds if the dummies had barring on their chests," said Dr. Welbergen.
"So if we made a cuckoo look less hawk-like - if we removed this bar pattern - it was more likely to be mobbed."
The findings showed that cuckoos could get better access to reed warblers' nests using "hawk mimicry."
Another study has also shown that birds lay parasitic eggs that are very similar in color to the host's own eggs, and that cuckoo chicks have evolved to mimic the calls of the hosts' offspring.