Great Northern Diver

Somehow I have not seen Great Northern Diver in Oxfordshire. Birds have often overwintered at Farmoor, in some years multiple birds. But all recent records were in my “Cuddesdon years”, when I was concentrating on my local patch, rather than county birding. Just before Christmas this year a juvenile Great Northern Diver was found on a small lake at Beale Park, just over the county border in Berkshire. In the first few days of January reports emerged that it was also feeding on the River Thames, just inside the county. Suddenly it got more interesting.

A quick look at a map revealed just how close to the border this bird was. The county boundary is the black dash-dot line that runs down the river:

The county boundary runs south on the right (east) side of the river until opposite Beale Park (“Wildlife Park” on the map above). Then, inexplicably, it crosses the river to run south, on the left (west) side of the Thames. The lake on which the Diver was first found is fed by a small stream that runs into the Thames at almost exactly the point that the county line crosses the river, just south of two small islands:

Below, Oxfordshire on the right, Berkshire in red, on the left:

So, for me to see this bird in Oxfordshire it needed to be on the River Thames, but south of the feeder stream from the lake in Beale Park. If it was on the lake, or on the River Thames north of the feeder stream, it was in the red zone, aka Berkshire, and was no use whatsoever for my county list. Having established the all important landmarks, I set out this morning to see where the bird was.

I walked up the tow path, passing a Little Grebe, a few Cormorants and lots of Siskins and found the juvenile Great Northern Diver on the river. It was reported to favour the area at the mouth of the feeder stream, but frustratingly, was north of this when I found it, so was in Berkshire. By about 8 meters. The views however, were superb:

It was diving frequently, but also spent some time just loafing, gently paddling against the northerly current, which kept it excruciatingly just outside of Oxfordshire. Surely, at some point it would just float over the invisible line and onto my Oxfordshire list?

It was a dark grey morning, with terrible light, but I took pictures of the bird as it surfaced between dives into the waters of Berkshire.

I was simultaneously enjoying being quite close to a Great Northern Diver and getting frustrated at its avoidance of my home county. Then, after about half an hour, a small group of rowers came up the river from the south. The Great Northern Diver took one look at them, dived deep and long and popped up behind them… in Oxfordshire!

Even more convincingly, it then spent some time well south of the feeder stream. I saw it as far south as the house on the east bank – a whole 250 meters inside the county! Tick.