A now relatively scarce farmland bird now more often encountered on heaths and scrub.
Yellowhammer: a little bit of bread
Yellowhammer in Dorset: what your tweets tell us ...
Fifty years ago the yellowhammer was a fairly common sight around farmland where it nested in hedgerows and fed mainly on the seed dropped during the harvest season. The change to winter wheat in the 1970s and a trend to hedge removal to accommodate larger and improved harvesters meant that both nesting cover and food supply for the yellowhammer, and other farmland birds of course, were lost and the population started to decline. It is estimated that in those fifty years the yellowhammer population has fallen substantially, probably by more than 50%, and this species is now missing from farms and found mainly on areas of scrubby chalk or limestone grassland. A yellowhammer is now something of a chance encounter rather than a species one would expect to see.
This is a resident breeding species in Dorset and the weekly reporting chart shows a small number of reports for most weeks of the year. There is possibly a trace of a small gap in August which would coincide with the annual moult. The number of reports shows a marked increase in October and November which suggests some autumn movement with birds from the colder northern areas moving south for the winter but in general it is thought British nesting birds do not move far even if they do move. A spell of severe weather will have an effect of course and drive even local birds to move in search of food.
There are records in the Nature of Dorset database from sixty two sites in the county and the distribution map shows a fairly close alignment to the chalk and limestone areas of the Purbeck coast and then up through the chalk downs from Bridport to the Wiltshire border. They are rarely found on heathland, never found in urban areas and they seem scarce on Portland.
It would seem a trip to Cranborne Common or Badbury Rings presents the best chance to get yellowhammer on to your Dorset list.