Dunnocks and tree sparrows come under the general heading of LBJ’s (Little brown jobs). Not a scientific classification, of course, but a catch-all term for a dull, little bird that you can’t quite identify.
Dunnocks are grey/brown little birds with sharp pointed bills. They tend to be solitary or in pairs. I see them more frequently than house sparrows both at ANR and the garden. Their song is quite melodious. Juveniles tend to be more speckled, rather similar to baby robins.
Tree sparrows are rather rare compared to the familiar house sparrow. I have seen them locally only at ANR where nest boxes are provided (top, middle image) and in the garden behind the visitor centre on the bird feeders. Both sexes have the same marking with a chocolate brown head and nape and a white cheek patch with a black centre. In common with many species the tree sparrow population had declined by 90% in recent decades but there are signs it is beginning to recover.
I’ve included pictures of house sparrows for comparison (male on the right). They share the same finch-like beak and the back/wing colouration is similar to the tree sparrow but they exhibit sexual dimorphism (Google it! 🙂 ) and the head marking is quite different. House sparrows are more abundant but they have suffered similar population decline to their rarer cousins.