I would have described the dunlin as a small wader that breeds in the Arctic but comes south in the autumn to spend the harsh winter months feeding on mud flats and could be expected to be seen at suitable sites along the Dorset coast between September and April. However, the sizable number of tweets in the Nature of Dorset database seems to contradict this statement, in part at least. A look at the weekly reporting chart shows that dunlin were reported from somewhere in Dorset for virtually every week of the year during 2017 and 2018 which almost makes it a 'resident' species. It does not breed here so why are there records for May through until August? There could be a number of reasons for this which might include:
- Some young birds may not be ready to breed and so do not make the journey north with the others
- Some birds may be not fit enough to travel the long distance to the breeding grounds and so choose to stay put
- Some birds may set off for the Arctic too early, find conditions unsuitable for breeding and so return south
- Some birds may start the breeding process only for their nests to be predated and so opt to return south rather than have another attempt
I have no idea whether these are actually valid reasons for the presence of dunlin in Dorset during the summer months and if anyone has knowledge that can shed light on this I would be delighted to hear it.
The weekly reporting chart, to my mind, shows up another interesting point. If many dunlin are spending the winter here in Dorset why do reports fade away during December, January and February? The chart shows reporting peaks in May and August and August will be the start of the major return here and so will generate reports as observers see the new arrivals and May could be observers reporting what they consider to be late staying birds so perhaps dunlin numbers are high during the winter months but are somewhat taken for granted and not reported?
One thing that is certain from the distribution map and the weekly charts is that during migration times in spring and autumn the numbers of dunlin are swollen by passing migrating birds and many will have just stopped off here before embarking on further travel north in spring and south in winter. I am sure many birds we see in August are intent on heading across the channel. The fact that they can turn up in so many places, some not deemed typical dunlin habitat must surely show birds that have stopped off for a break in their journey.
It is quite remarkable that the vast majority of reports come from just two sites, Lytchett Bay and Ferrybridge; these are both well watched and recorded sites which probably accounts for it but with suitable mudflat habitat in Christchurch Harbour and around the eastern borders of Poole Harbour why are there so few reports from there? There are certainly good numbers of dunlin around Stanpit in Christchurch Harbour and on Brownsea and at Arne in Poole Harbour.
If you want to see dunlin the reports suggest Ferrybridge and Lytchett Bay are the places to go especially in the autumn and early winter.