He was like our pet bird for a long time. Fed and cared for during the winter, protected by the Rottweiler during the summer from neighbour's cat.
But since a few months I could observe that the tits did not even fly away when Clyde was standing next to them. At first I thought it was habituation but now studies have been published in Germany claiming that tits are also dying en masse from some kind of pneumonia.
Bacterium Suttonella ornithocola causes death of blue tits.
(Text in German)