Well I've never seen an immature Robin before but I have read in my Book of Irish brids that they have speckled breasts. This Robin had a strongly coloured red breast but with a speckled belly or underneath. The Robin was also big, bigger than most Robins I've ever seen. Was it a Robin, an immature Robin, a immature Robin growing up (wrong time of year for that?) or another Bird altogether?. I wasn't able to get a photo of it but I'll keep the camera by the windowsill in future...