Black-throated Diver, Stocks Reservoir, Lancashire, 10/10/2000.

By Bill Aspin.

This bird was seen 6 times (between dives) during a 15-minute period in inclement weather conditions.

The overall impression was of a contrast bird, black above and white below with a long, low body profile and a white rear flank patch which, due to the rough water state was most noticeable when the bird either dived or when the birds body was lifted up on a wave.

After 15 minutes the bird was eventually lost to view as the weather worsened and was last seen 'steaming' out of view in the direction of dam end of the reservoir.

After this final sighting, the weather almost immediately and rapidly improved, but it was another 45 mins before an attempt was made to relocate the bird at the other end of the reservoir.

Subsequently, and to my utter frustration, attempts to relocate it were unsuccessful despite extensive searching and it appears the Black-Throated Diver took advantage of the rapidly improving weather and departed unseen.

Description.

Head+Neck : Due to the nature of the strong wind/choppy water, the bird was forced to tilt it's head at an angle, upwards, not unlike a R.T. Diver, however, the bill was straight and slender with a darker upper mandible, contrasting slightly with the greyer lower mandible. The headshape was nicely domed and the head and neck were contrast black and white, the division of which was below the level of the eye and sharply demarcated. The cheeks and foredeck were white and the sides/rear of the head/neck were dark.

Body : The upper parts were dark. When the bird dived the flanks could be seen to be white. The division between the upper parts and under parts along the flanks was straight until the rear flank area, which showed a distinct white flank patch 'bump' .

  Age : I couldn't discern any pale fringes to the upper part feathering, as views were not that close and as a result cannot age the bird with confidence. However, I feel that the sharp clean demarcation on the head/neck does probably eliminate the bird as being a juv.

It is therefore probably best to say that it was in 'non-breeding plumage' (i.e. adult/imm).

Accepted by the Lancashire Records Committee,