It was a grey go-away bird. (formerly grey lourie)
You can find a picture of the grey go-away bird in the Africam Birds Database
It gets its name from a belief that the go away bird (grey lourie) sits in the tree and warns the other animals of any aproaching cats, the call sounds like it is saying "go away go away" It likes to eat fruit and flower buds and new leaf buds.
Thanks Katja, I will look it up