Saturday, 2 July 2016

Catching on

An early morning visit to Motney, a late evening visit to Ham Green, mostly thinking about Oystercatchers. I've mentioned  Oystercatcher movements within the inner basin in general terms already, so a little more explanation of what goes on in the outer basin might be appropriate now. 

At the lowest point of the tidal cycle many Oycs will be feeding on the large oyster beds found in the Ham Ooze area. As the tide covers this stretch early the birds retreat mainly via Millfordhope Creek, sometimes heading straight to the Chetney Hill roost, often detouring into Twinney and Halstow creeks to take advantage of the additional feeding time. Eventually all these birds also move off to Chetney Hill, where they are joined by Funton feeders. On higher springs the roost might move to the old dock below the hill, but if disturbed by walkers then inland to the fields. Sometimes a small roost can sometime be found inside Barksore as well.

Then there's the Deadmans Island roost. This picks up local birds, but is also a refuge for Thames Oycs under certain conditions. On spring tides their usual Grain beach roost site can go under. At other times it suffers disturbance (at present there is no official footpath there, but walkers and fishermen often visit) when Sometimes these birds might head for Yantlet or another nearby beach, but more often they head south-east and south into the Medway to Deadmans. Back in the early nineties Grain was my 'patch', and in the 25-odd years since their dependency on Deadmans has grown. Simple fact is Yantlet can be one of the more disturbed roost sites. East of Grain, The Flats and Grain Spit are excellent feeding areas, and viewable from Deadmans. The flight might be longer, but it is a good, safe choice.

Right now it's time for Oystercatcher numbers to increase. Certainly most immigrants from the continent arrive in August and September, A rough and ready guide to numbers using these three core areas outside the 'wintering' months?

In the 1990s four-figure counts for the whole of the estuary in May, June and July were usual, but by the turn of the century counts had become erratic and incomplete. Of course, it does not help that birds change roosts (and rivers) but since returning in 2013 my counts in each ten-day period are pointing towards the present usage being more in line with the good old days. The graphic includes the Thames birds in blue, so as to give an idea of numbers feeding in the southern Medway. If you were then to add in the known main roosts on the northern shore (the Kingsnorth Power Station sea wall under certain conditions, and more routinely Oakham Marsh) then four figure on co-ordinated counts for the whole estuary should be achievable.

The casual birding visitor might miss out on all this; it has taken me a few seasons to catch on fully. With the main oyster beds being some distance from shore, and Oystercatchers prone to being one of the first species to go to roost, a birder might pick up on the thin spread of birds, sometimes in pairs, close in to the sea walls. Some will be breeding pairs, but there are not as many as one might at first think; sexually mature from around three, but possibly not breeding until four, five or later, places like Horrid Hill are a 'back of the bike sheds' for some Oystercatchers. Optimal breeding habitat is thin on the ground, and pairs are often found on the brownfield areas. Mid-river, the concrete jetty out to (and beyond) Oakham used to have a number of nest trays, lovingly re-shingled each year by the Power Station Environmental Officer after he discovered the birds would try and nest among torn lagging on the pipework. The photograph is from 2012- whether they are still in use in 2016, who knows?

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