SOME birds learn to recognise members of their own species by comparing
feathers.
Most birds learn to identify their species by studying their nestmates and
parents. But parasites such as cuckoos and cowbirds are reared by complete
strangers, so they must have a different system.
Mark Hauber and his colleagues at Cornell University in Ithaca, New York,
used ink to darken some feathers of 21 hand-reared cowbirds. At two months, the
darkened juveniles preferred to associate with adults who had similarly darkened
feathers, but avoided normal-looking cowbirds (Animal Cognition, vol 3,
p 113).
“Visual cues such as feather colour learnt from your own body may…
