Wren

While only slightly smaller than the UK's smallest bird (the goldcrest), the wren is much easier to find. This is both due to its abundance and behaviour. The wren is the UK's most common bird, with an estimated 11 million pairs spread across various habitats. It has a distinctive song that it sings while patrolling perches within its territory and tends to switch to a higher perch during each pause. 

If a wren is heard by a wildlife photographer but the view is obstructed, the photographer can simply wait patiently for the bird to continue its song from a higher, more isolated perch. In fact, that is exactly how this shot was achieved!