Thursday 16 December 2021

Great Northern Revisited 15th December 2021

In the usually unexceptional days of winter at Farmoor the arrival of a juvenile Great Northern Diver has brought some very welcome excitement to the reservoir and I determined to make the most of the opportunity, returning early this morning for another spell of watching it go about its life. A dreary and dull morning of low cloud and grey horizons could not dampen my expectation as I made for the central causeway.

I was the only person on the reservoir and soon found the diver in its favoured corner of the smaller reservoir basin, where the causeway begins and from where the diver progresses, in a series of feeding dives, roughly parallel with the causeway to almost the far end and then back again.

The diver came close to the causeway on many occasions and watching it surface it became obvious that each time it did it would bring up strands of weed, called silkweed, wrapped around its bill and presumably garnered underwater as it pursued the fish that hid there.The weed is long, very thin and can look superficially like fishing line, causing some concern to various observers, unaware it was only weed and the diver was suffering only a minimum of inconvenience. It was obvious the weed was an annoyance when it surfaced with the thread thin strands wrapped around its bill but it always managed to shake the worst of the weed off with a waggle of its head or by dipping its bill in the water.

Great Northerns usually consume whatever they capture while underwater, unless the prey proves too large, in which case it is brought to the surface to be dealt with. It is rare on the reservoir for any fish to be brought to the surface by a Great Northern Diver as those captured are usually small enough to be consumed underwater but on one occasion this morning the diver brought a sizeable Perch to the surface to be subdued and quickly eaten, which was a first for me.

I wandered along the causeway, a stop start progression following the diver, trying to anticipate where and when it would next surface. Sometimes I was right and at other times not. It was however an enjoyable  exercise of guesswork and anticipation as where to move to stand and wait, while the diver was below the surface.

Towards the end of my time in the company of the diver it seemed to have settled to feed in one particular area of water about a third the way along the causeway and surfaced repeatedly here, offeriig great photo opportunities which inevitably attracted a number of visiting photographers. And why not? 

Such opportunities do not come every day and this diver in particular was very obliging in this respect.

Although unplanned, I kept with the diver for the entire morning and quite naturally such a concentrated period of observation led me to an awareness of various other aspects of its behaviour. For instance whenever a Cormorant or Great crested Grebe came near, the diver would lower its head to almost water level and position itself pointing towards the intruder.That was as far as the threat went and I never saw it actually pursue either bird although it would maintain this position until it felt the offending bird had distanced itself sufficiently

When about to dive it signalled this by lowering its body in the water, often with water washing over the base of its neck, compressing its feathers and taking on an angular almost reptilian appearance.

When not feeding the diver would swim further out onto the reservoir and idle there, dozing, its eyes closing briefly as its bulky form floated in repose on the water. Doubtless the feeling of being secure at such a distance made it feel relaxed enough to preen,  which it did by rolling onto its side and displaying a pristine white belly, that even at a distance gleamed, beacon like in the dull light of midday. 

Memorably there was an occasion while preening, where it extended its leg and foot, the extraordinary size of its webbed foot thus displayed and clear evidence of what propelled and provided the power for the underwater pursuit of its fish prey.The extreme positioning of its legs at the end of its body was also clear for anyone to see.

On such an un-auspicious day of weather the diver brought a ray of light to the grey gloom of this unseasonably mild weather.

I went back the following day and the weather was pretty much the same until early afternoon when by chance the sun shone through the blanketing cloud for an all too brief few minutes.

The diver was transformed in the sunlight.

And some more images from when the sun did not shine but the diver still looked splendid

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