The completion of the first detailed look into the relationship between New Zealand’s shining cuckoos and grey warblers suggests that the cuckoos have have escalated the ‘arms race’ common to co-evolution.
An excerpt: (read in full here)
“Contrary to the idea of co-evolution, the shining cuckoo has developed prowess as an artful mimic, while the grey warbler does not appear to have altered its begging call at all.
“Anderson recorded the sound properties of nestlings of native forest birds around New Zealand, and, not surprisingly, found species that sounded more similar to each other were usually more closely related. But the shining cuckoo has altered its begging call to match its host, the grey warbler, despite not being as closely related to it as other birds.”