Rissa tridactyla – GWYLAN GOESDDU – Breeding resident and passage migrant
Comparison with previous atlas:
|Breeding possible||excluded from total||excluded from total|
|No of tetrads occupied||7 (of 478)||6 (of 490)|
|Percentage of tetrads||1.5%||1.2%|
Kittiwakes nest in dense colonies on ledges of vertical cliffs. Although now almost totally confined to the islands of Skomer, St Margaret’s, Grassholm and Ramsey, they were formerly very common coastal breeding gulls, especially along the Castlemartin coastline to Stackpole Head. Kittiwakes have never nested on Skokholm.
These changes in the breeding colony sizes and distribution have been dramatic and largely remain unexplained, for whilst the Skomer population has remained relatively stable at around 2,200 pairs, other colonies have disappeared completely. In the period following the Seabird survey of 1985-87 the thriving colony on St Margaret’s Island reduced from well over 300 pairs to just 6 in 2000, and then increased again to over 300 in 2009. This quite rapid change must include some birds which have moved from other breeding sites. Along the Castlemartin peninsula a population of around 700 pairs during 1984-88 had declined to about 30 pairs by 2007.
Overall the Kittiwake population has declined significantly in the county in recent times. Between 1969-1970 and 1985-1987 surveys the county population increased from 3,037 to 3,935 pairs but had subsequently declined to around 3,100 pairs in 2000 and had probably a similar population total in the period 2003 to 2007.
The breeding success on Skomer is variable with productivity ranging between 0.30 and 1.01 chicks per pair but generally near to 0.5. It is a low level of success and there is a “feeling” that, as at many other colonies around Britain in the first decade of the 2000’s, Pembrokeshire colonies have suffered breeding failure and a rapidly declining population is just about “hanging on”.