The hobby is famed for following flocks of migrating hirundines on migration with the small birds providing a constant supply of in flight meals for the predatory hobby. The hobby is also famous for its ability to catch dragonflies in mid-flight, quite a remarkable achievement. Both of the these features I think show through in the reported sightings of these spectacular birds in Dorset.
The hobby is a summer visitor to Britain and they start appearing in Dorset from week 13 in early April but the main influx of spring birds seems to occur from week 17 in May to week 24 at the end of June. Many of these early reports will be of birds moving through to more northerly locations but some will nest in Dorset hence reports throughout the summer before autumn migration picks up in August with the peak for reports coming in September and with them all gone by week 43 in mid October. September is, of course, the prime time for migrating swallows and martins which must contribute to the increase in hobby sightings at this time of year.
The bulk of reports come from Arne, Hartland Moor, Radipole and Morden Bog and these are all sites where dragonflies occur in good numbers throughout the summer and autumn which must have an influence on their presence in these places both during the breeding season and on migration. Juveniles have certainly been seen at Morden Bog and at Radipole which is a pretty good sign of successful breeding in these areas.
The distribution map shows how widely dispersed sightings are but the highest density seems to occur in east Dorset and in Purbeck where there is extensive heathland with heathland ponds and bogs which is where dragonflies are at their most numerous. There are also several reports from locations along the Fleet where they are most often seen arriving on migration or spending a day or two feeding before setting off across the English Channel on their way south in autumn.
Being primarily migratory in Dorset is difficult to predict where you might see one but the most likely way to add hobby to your life list is to go to Morden Bog in summer and watch the bog pools where hobbys can often be seen hunting for dragonflies.