Pipits in trees are usually tree pipits (Anthus trivialis), just like this one. They are very similar in appearance to the meadow pipit so their different calls and their preferred habitats are important in identifying them.
An occasional species of open heath with a scattering of trees and bushes with a generous helping of bracken.
Tree Pipit: in free fall
Tree pipit in Dorset: what your tweets tell us ...
Whilst the tree pipit is a breeding species in Dorset it does not seem to be numerous or widespread here. Its preferred nesting habitat is heathland, moorland or wooded commons especially where there are conifers present so the Dorset heaths should be prime territory for them and that is where the bulk of our nesting birds are seen. The tree pipit is a summer visitor to Britain and is certainly far more common in Wales and Scotland than Dorset and so there is a significant amount of passage migration of this species through the county in spring and autumn of birds making their way further north to breed and then returning south to central Africa.
The weekly reports on Twitter suggest that early arrivals can be seen from week 12 in late March but the bulk of the inward movement seems to be during April. Numbers fall off from week 18 but with a peak in week 20 in May which may coincide with males singing on territories. Weekly reporting levels during the summer months are generally quite low with a gap from week 28 to week 30 during July. This gap can be seen in other summer visiting migrants too and I suspect that it coincides with the moult when birds are generally less visible. The autumn exodus seems to occur mainly in August in weeks 34 to 37 but reports continue to come until week 41 with a few late birds leaving at the beginning of October.
Forty five sites in Dorset have reported tree pipits. These locations seem to divide in to two groups with the heathland in the east of the county and in Purbeck seeing a good number and many of these will be breeding birds as this is where much of their preferred habitat is. The other group of sites are along the coast from Portland to Lyme Regis and these will, in general, be where passage migrants will be seen.
A visit to Morden Bog or Arne in May is likely to to produce a tree pipit for your Dorset list.