WI - Cormorant Research Group News 13-09-2001

[UK1] News from the Abberton Reservoir.
Graham Ekins, UK Cormorant Colour-ring Coordinator, Boreham, Essex, UK,

Today (22/2/01) at Abberton Reservoir (51.49N00.51E) I did my fortnightly count of nests. A total of 137 nests were occupied, 76 of which were being incubated. Interestingly 12 of the females had already started to lose their headplumes, it normally takes three weeks for the females to totally lose their head plumage. This "spring" I had a number of males in full plumage back in the colony displaying on some of last years nests on the 21st December. In this colony the peak number of nests was in 1996 with 551 pairs, last year the total was 356, the fourth successive decrease. The average brood size has also decreased over the same period. Last spring I found several nests with young that were emaciated suggesting that food availability rather than available nesting sites was the reason for the decline. So far Abberton colour-ringed birds have been found nesting in 7 other UK tree-nesting colonies plus one in Belgium and 2 in The Netherlands. So far none have been found in coastal carbo colonies. Genetic studies have shown that they are a mixture of both carbo and sinensis. Pure examples (colour and metal-ringed) of sinensis and carbo have been found nesting (from Belgium, The Netherlands, Denmark and Sweden-all sinensis; plus carbo from Saint Margaret's island, Dyfed). Recently a colour-ringed bird from Abberton was seen in The Netherlands and reported as a carbo. Although this bird may have been morphologically identifiable it is very unlikely that it was genetically all carbo. The only certain way in my opinion to identify pure carbo would be to find a colour-ringed coastal nesting bird from Norway, coastal UK or coastal NW France, as has recently happened in Belgium.