Sunday, 21 January 2018

Lord of the Ringos

One Ringo to rule them all,
(one Ringo to fight him),
one roost to make all safe,
 and over high tide bind them.

(J.R.R. Thornton, 'Birds of the Mordor Estuary')
- - - - -

Sometimes things just come together. Watch a behaviour, make a considered guess, then find the reference in 'Birds of The Western Palearctic', or similar. Had puzzled over this the past couple of winters, watched it play out the past week.

The Ringed Plovers are on the move. Not migrating, just displacement within the estuary. Many hold a feeding territory, and those close to the footpaths can be almost guaranteed. Right up until the time the Dunlin hordes begin to increase their feeding periods on the higher flats.

Ringos, just like many of the Plovers, feed mainly by sight, employing a watch-dash-feed technique. They can put up with some inter-species close competition, but as numbers grow, feeding disturbance grows as their prey retreats from increased vibrations from all those feet and bills.

This past week Ringo numbers around Rainham Docks East and Sharps Green Bay have dropped as Dunlin numbers have gone up. At the same time numbers have increased short distances away, at Copperhouse, Bloors and Otterham. This morning three Ringos disputed ownership of the creek right in front of the north-west corner of Bloors. After an hour or so's chasing, two held the banks, one had retreated out towards the wreck of PAS1511.

One quick read of 'Birds of the Western Palearctic' later, and things fall into place. Studies at Lindisfarne had shown this to be a routine behaviour.

WeBS in past few years has had a Medway peak in February. This could only be true if there was a regular mid-winter influx. Studying the excellent graphs available on the WeBS link (poor screengrab below), it is apparent this has not been the case at local or national level. My own records reflect a species most numerous during the passage periods with steady winter numbers, albeit slightly higher in the second half of a winter.

Now why would that be? They like sandier flats, and several of these extend out to the centre of the estuary. In better feeding weather, it could be birds can obtain enough food further out. It might be there is a slight adjustment by birds feeding on the mid-estuary flats moving shoreward. As they have to 'make do' in the face of high calidrid numbers, they might well have to take up more sub-optimal areas, and switch to closer roosts? They are certainly easier to find now during the low tide cycle, with a lot more picked up on call as they dispute new territories.

The international threshold stands at 730; the Medway numbers are nowhere near that. But with in excess of 225 present along the southern shore, from personal knowledge the actual estuary winter population routinely nears, perhaps breaks, the GB threshold of 340.

Why any counts of Ringed Plover for the various individual sites around the estuary can be really useful.

Before leaving, worth looking at Low tide counts (available from the same excellent link):

36 is an extremely low result, and in no way representative of the true numbers on the estuary that winter; even when uncounted sectors (grey) are considered, many more birds were found during the intertidal periods.
Previous results can also be seen via the webpage:
   2005/06-  30     /  17   /  0.05
   2004/05-  332  /  122  /  0.08
   1996/97-  442  /  315  /  0.05

If present counts are correct, that drop in 05/06, and the most recent partial count do not represent the population here.

For further info on the southern Medway's roosting Ringed Plovers, try my previous blogposts here (numbers) and here (disturbance).

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