Do Blackbirds Mate With Thrushes?

Although it is theoretically feasible, it is very rare that a thrush and this species would ever breed. What you're describing, Derek, is exactly what I've been used to seeing in the younger generation of people that come to my garden here. They initially have a very brown appearance, similar to that of a female but with specks. After that, their main feathers and tail become black, and then their back does as well.