A summer visitor to woodland edges and scrub areas
The willow warbler (Phylloscopus trochilus) is a summer visitor to Dorset; a classic migrant species that spends the British winter months in Africa before making the long journey north for the summer to breed and then returning south in the autumn.
The chart of weekly reports shows what I think is a classic summer migrant profile with a surge of reports in spring as birds arrive then a quiet period with few reports despite many birds present and then a further peak in the autumn as they depart. There are probably a number of reasons for this. Firstly, many of the reports are from ringing projects who will be trapping these birds whilst on migration and secondly, obviously perhaps, the numbers of birds in Dorset will be far higher during migration periods than the numbers here during the breeding when just those nesting will be present. A third factor could be that the sites where willow warbler breed are probably less closely monitored than the coastal sights and the coastal sites are where migration, and so the number of birds, will be more obvious. I think also that the nature of the recording process I am using by monitoring tweets influences the distribution in that reporting the first willow warblers of spring is newsworthy but then, as the species is quite common, seeing a willow warbler when out for a nature walk becomes routine and un-newsworthy.
Despite the possible flaws in the recording process I have outlined, the weekly chart does show a pretty true reflection of the willow warbler's presence in Dorset. After early reports in March there is a surge in weeks 16 and 17 (mid to late April) and that is obviously when the major influx of arrivals can be seen. Reports quickly fall away through late May until early August when the first signs of the exodus become apparent and the bulk of the birds seem to be leaving around week 34 and 35 (late August). Unlike some other warbler species, notably the chiffchaff and the blackcap, there are no records in winter, the latest records come in week 40 so this implies there is no inward traffic from northern Europe to over winter here.
The distribution map shows how widespread the species is in Dorset but, as I said above, many of the coastal sites will be migration sightings whereas many in land sites are woodland and are likely to be nesting sites.
To find a willow warbler I suggest going to any broadleaf or mixed woodland in early May and listen for its lovely cascading song; you will need to learn the song first of course.
|Common Name||Willow Warbler|
|Scientific Name||Phylloscopus trochilus|
|Species Group||Birds Warblers|
Bird sat high in a tree singing a cascading musical song
|Additional Identification Notes|