Mrs Blackbird.

Busy digging for nesting material in the large pot near our back door which contains two roses. Each morning she comes and does some gardening and scatters compost in all directions. We don't mind as it is good to see them in the garden. Female Blackbirds build the nest, the male does guard duty, he is very alert for any possible danger. 
They seem to choose the nest site together, but this is just a guess on my part.