For most birders down the years, the Ordnance Survey has been their guide to patch boundaries, and the Medway has ended somewhere between Sheerness and Grain. If you check the annual county reports, totals for birds such as Common Scoter have often just referred to counts as being at Grain. Historically, the ease of parking and the lure of adjacent bushes has dragged visitors to the north shore; very few birders have enjoyed the concrete of Sheerness- if you've made the effort to visit Sheppey for birds, then Warden, Leysdown and Shellness will always drag you to east.
When I birded Grain through the nineties, the Ordnance Survey told me of the Roas Bank and the Flats. At the time, most birders just called the whole expanse the Roas. The older OS maps had made more of the Flats, with the Roas being a small area north of the village. Depth readings today show no raised bank; it is still there, an area of much more solid mud (I have walked it once, and that was enough), but the modern navigation maps have dropped it.
The other advantage of the navigation maps is the offshore detail- excellent sites such as i-boating allow you to see what the seabirds can see; the deep water channels. Seabirds love 'em. On the screengrab you can see how the Thames has a clearly defined channel cutting close to Canvey island; why they get close silhouette views of Skuas, why Kent birders see clear but extremely distant shearwaters (and why the two county annual reports have different totals/mixes for such species most years- as one local birder always argues, the two counties really need to be talking to each other more).
But I digress. The tentacle that is the Medway deep water channel is extremely clear; for sailors, the tidal effects can felt some way offshore (the first maker buoy is highlighted above), and why, some birds moving past Sheerness can be said to be using the channel.
Politically, the boundary between Medway and Thames is an imagined line between the main bastion of the old Dockyard at Sheerness, and the church tower at Grain. It appears on the navigation maps, and is hinted at by marking the local constituency boundary through the estuary.
...but Roas and The Flats have made way for Grain Spit and Yantlet Flats.
Drawing the imaginary boundary line makes for a very convenient marker on the shore, just a couple of metres shy of where the boundary hits the seawall; the old concrete lookout, a shelter for many a long seawatch (circled in red).
Nowadays my visits to Grain are few. Back in the day, fair weather meant watches north of the village, overlooking the Thames. No sane birder would choose this blockhouse. Or the benches above it, just south of the Moat at a height of five metres, or atop the Moat itself, some ten metres above sea level (both good spots to listen for the wandering tit flocks to break the monotony). All a short walk from the Chapel Lane car park (blue). But if I'm there nowadays, I'll try these for their views out to the Medway Channel.
And you really have to have a sad Medway fixation to want to watch due east, when many more birds are following the Thames just north of you; this morning's clear sky beyond Sheerness would have most giving up in minutes.
All good reasons not just to keep lists. Take Common Scoter. Today a small group were picked up high off of Jacob's Bank (north and west of Sheerness). Clearly following the shoreline. As the reached the Medway deep water channel they dropped low and turned south-west, in and past the Tower. And they used it like a race marker, arcing behind it and heading back out north-east down the Channel, to put down out around the Great Nore. (More on that species in my next blogpost.)
So, what lists could those Scoter have ended up on today? Grain? Tick. Sheerness? Tick. Thames? Tick. Medway? Tick. None of which tell the story of how this dog-legged narrow Channel puts off seabirds from venturing further into the Medway estuary. All helping confirm the Medway's rare position of 'inland estuary', ornithologically speaking.
A final postscript; the Grain warm water outflow steams once more! Certainly the gas-fired flow and temperature may be somewhat lower than the old oil-fired station, and not likely to bring a repeat of the glory years of Tern attractions but it was enough to lure Cormorants and a Shag into the mist this morning. Who needs Dunge, eh?