Sun, 16th Sep 2007
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from the show The Best of the BA Festival
Richard Hawkins, Napier, New Zealand asked:
I've got a small aviary at home with several different species of birds in it, and every so often when I have to add another one there, because of natural losses, the different birds always seem to know what they are, the budgies don't try and mate with the canaries and the finches don't try and shack up with the canaries. I was wondering how they actually knew what they were, and I assumed it was just how they were brought up by the parents. It then did occur to me that how on earth do cuckoos manage? Cuckoos, being brought up by a foster parent of a totally different species, eventually grow up and spend a life as a cuckoo, behaving like a cuckoo and finding another cuckoo to mate with.
This question was answered by Dr Karen Spencer, a David Phillips Research Fellow at the University of Glasgow
The case of the cuckoo is a really interesting one, because originally it was thought that they were pretty much impervious to this imprinting mechanism [when a young bird learns to identify it's parent and act in a similar way, it is said to have imprinted on the parent] and they could ignore the visual, acoustic and social interactions with their foster parents, and they just innately knew, genetically knew who they were, and could basically ignore all environmental inputs.
Recently it has been suggested that isn't quite the case, there's still a lot of questions to be answered certainly in this, but there is some evidence that in some species adult cuckoos visit the cuckoo chicks just before they're about to leave the nest. Now this means that they can then, obviously, imprint on this adult cuckoo but it still raises the question as to whether they've actually got a genetic filter to stop them imprinting earlier on, on their foster parents. Now if you take a cuckoo chick away from any other cuckoos and put it in a nest, and it grows up and doesn't actually get this later input from a cuckoo, it does seem to be slightly confused about who it is. It doesn't necessarily imprint totally on the foster parent, but it does have a few social problems when you introduce it to another cuckoo.