Visible migration; Horrid results for the finches

The question- is visible migration worth studying along the south Medway? The results from this year's early morning counts at the point of Horrid Hill (plus, from early October, a second spell on the Mound at the base) have provided some useful support to findings made at other sites on the south Medway since autumn 2013.

The opening quotes for each species are from John Holoway's 'Birds of Gillingham', and then Dave Davenport's chapter on migration from Oliver's 'Bird watching on the North Kent Marshes'. The graphs are this years Horrid Hill figures, whilst the maps, unless otherwise stated, are based on cumulative observations for the whole southern shoreline over the past five autumns.


Chaffinch

Holloway (1985): "..flocks are often seen along the river and on farmland in autumn and winter.."

Davenport (in Oliver, 1991): "..last three weeks of October and first two weeks of November produce the main westerly passage.."

Chaffinch has been an eye-opener for me for many years since first bumbling into the factoid that the majority of 'finks overwintering in the U.K. enter via the south-east (unlike Bramblings that mainly come in further north).

It is certainly a great example of east-west visible migration here. Previous autumns, east and south-east of Horrid, have shown just how strong that movement can be. Often the biggest counts happen the day after east coast sites such as Pegwell have their big arrivals, as if they are putting down within an hour or so of crossing the Channel.

Brambling

Holloway (1985): "..occasionally seen with Chaffinches in the winter months.."
Davenport (in Oliver, 1991): "as Chaffinch.. accompanied by smaller numbers.. main arrivals equally likely to occur in early November.. frequently associated with hard winters.. when.. takes to feeding on the saltings or along the sea walls.."

A species that never regularly turns up in numbers in the autumn, one that is more prone to see cold weather movements later in the year. Whether these later movements are from birds already in the UK, from the north, or further immigration from the near continent, is difficult to say. The autumn birds here are tied in with the onshore Chaffinch pulses and should be considered as 'fellow travellers', as the majority of Brambling arrivals come in over the northern North Sea.

Greenfinch

Holloway (1985): "..widespread.."
Davenport (in Oliver, 1991): not mentioned.

Another species many believe comes over in numbers, but one that ringing evidence says 'no'. Certainly these grounded birds were only coming out to the Point on Horrid to feed; stay long enough and you would see them return to the same spot on the 'mainland' most days. Any peak could just as likely be down to local dispersal.

Goldfinch

Holloway (1985): "..fairly common.."
Davenport (in Oliver, 1991): "..increasing numbers (in October).."

Although the past few years have picked up a definite 'southerly' feel to autumn flights, perhaps indicating a larger element of emigration rather than immigration, the local topography creates a south-west movement inland. Goldfinches at the Point are more likely to be coming in from a northerly vector than most finch species reviewed here.

In previous decades wintering numbers were much lower, so picking up movement late in the season was easier, but there are now several areas where Goldfinches remain in fair numbers throughout the autumn; local ringing has shown some local breeders to be sedentary. To that end, daily roost flights have to be considered when considering possible viz mig; these roosts grow in size from early September onwards.

Linnet

Holloway (1985): "..can be seen along the Medway at any time of the year.."
Davenport (in Oliver, 1991): "..on some October days.. southerly movements of Linnets.."

Very similar general comments to Goldfinch, with a nice southerly trend to flights. However, many more feeding flights to the island saltings, so difficult to pick out viz mig; roosting habitat preferences, such as dense bramble, are not found on many of the islands and the short duration of the main southerly pulse points towards an ability to pick up on viz mig.

Siskin

Holloway (1985): "..very uncommon migrant but in October 1983 there was a large passage.. flocks of 20 or so could be seen flying west.."
Davenport (in Oliver, 1991): "..last three weeks of October and first two weeks of November.. season for (large visible movements) accompanied by smaller numbers of.. Siskins.."

No shocks with this graph; not a Siskin autumn. This species (and the following) have a large element of irruptive nomadism to their seasonal movements. Irruptive, because they work from local food source to local food source- there is no promise of food at the end of a long migration to the same spot as the previous winter; why, for example, Scandinavian breeders might first move south then possibly move west, or east, later into the winter.

Lesser Redpoll

Holloway (1985): "..occasionally seen with other finches in winter.."
Davenport (in Oliver, 1991): Not mentioned.

Siskin and Redpoll could almost be lumped for viz mig comments. Again, feeding further north must have been good at the start of the autumn (ringing has shown that many birds in the south-east in autumn have come from within the UK).

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In conclusion, diurnal movements of finches, although nowhere near as strong as along the Thames, itself nowhere no as strong as further east in the county, is observable on the estuary, and regular watches can turn up the odd 'big day'. Even if these results don't fill you with any urge to rush to the Medway, bear in mind the Thames is woefully under-watched these days; despite the adverse comments places like Grain seem to receive on an annual basis on social media, the birds are still passing there. Lower Hope Point at Cliffe, Allhallows, Sheerness on the island, all spots where viz mig awaits to be recorded fully again.