Oct. 16, 2013 — New research shows that cuckoos have striped or "barred" feathers that resemble local birds of prey, such as sparrowhawks, that may be used to frighten birds into briefly fleeing their nest in order to lay their parasitic eggs.
By using the latest digital image analysis techniques, and accounting for "bird vision" -- by converting images to the spectral sensitivity of birds -- researchers have been able to show for the first time that the barred patterns on a cuckoo's breast may allow it to impersonate dangerous birds of prey. This might enable cuckoos to frighten other avian hosts into leaving their nests exposed.
The latest findings, published today in the journal Animal Behaviour, expand the cuckoo's arsenal of evolutionary deceptions, which include egg mimicry and chick mimicry that allow it to trick other birds into incubating its eggs.
Importantly, the study shows that a wide variety of cuckoos have adapted different plumage patterns depending on the area they inhabit so that they match a local bird of prey species.
While scientists have intensively researched links in plumage patterns between the common cuckoo and Eurasian sparrowhawk, the new research shows that this type of impersonation of a more dangerous animal -- called 'Batesian mimicry' -- may be far more widespread in cuckoos. In addition, the dangerous bird of prey that cuckoos resemble goes beyond sparrowhawks to include such raptors as bazas and harrier-hawks -- depending on the species prevalent in the cuckoo's neighbourhood.