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Seabirds

JNCC Seabird 2000 and Seabird Research on St Kilda

During May, June and July 1999 a team of ornithologists took part in a census of the seabirds breeding on the islands of St Kilda. The expeditions were led by scientists from the Joint Nature Conservation Committee (JNCC), the British Government's advisor on nature conservation. The last major census of St Kilda's seabirds was conducted in 1987 and the 1999 census formed part of a larger project, Seabird 2000 , which aims to count all breeding seabirds in Britain and Ireland.

The islands of St Kilda hold over half a million breeding seabirds including the world's largest northern gannet colony of over 60,000 pairs. The table below shows the counts from the 1999 and 1987 census for some of the species present. Every single pair, bird or nest (depending on species) was painstakingly counted. This was particularly arduous on the eyes when counting fulmars, which appear as white dots peppering the massive 300m high cliffs. While the majority of birds on the main island of Hirta were counted from land, accessibility problems meant that counts on the other islands were conducted from our two survey vessels, the MV Cuma and Poplar Diver. Looking through binoculars from on board a boat rolling on the North Atlantic swell proved not only difficult at times, but also uniquely nauseating.


A comfortable perch from which to count seabirds on Hirta's huge cliffs
Photograph: Ian Mitchell

Working in pairs to minimise errors, surveyors counted every single one of the 64,842 pairs of fulmar that cover the cliffs of St Kilda
Photograph: Ian Mitchell

Of those species not listed in the table, gannet were last counted from the air in 1994 by the Centre for Ecology and Hydrology as part of a 10 yearly survey of all Britain's gannet colonies. A start was made in 1999 to survey the other species, puffin, Manx shearwater, storm petrel and Leach's petrel, and a second expedition in 2000 will aim to complete counts of these four burrow dwelling species. While puffins are diurnal, the petrels and shearwaters are nocturnal and so in order to count these three species by day, sound is used rather than sight. Taped recordings of petrel and shearwater calls are played in suitable nesting habitat, to which nesting birds will respond by calling back. This will be the first accurate census of these three species on St Kilda. In particular it is important that we determine how many Leach's petrel breed on St Kilda, since only several hundred pairs breed elsewhere in Britain and St Kilda is probably the largest colony this side of the Atlantic.

 


Counting the thousands of puffin burrows, which pepper the steep grassy slopes of Boreray
Photograph: Ian Mitchell

Species 1987 1999
Fulmar 62,786 64,842
Shag 52 20
Great Skua 52 163
Common Gull 0 1
Lesser black-backed Gull 154 25
Herring Gull 59 6
Greater black backed gull 56 10
Kittiwake 7,829 3,886
Guillemot* 22,705 23,457
Razorbill * 3,814 2,545

Numbers of breeding seabirds on St Kilda in 1999 compared to the last count in 1987. (Data: JNCC)

*     (figures for guillemots and razorbills are counts of breeding adults, whereas all other figures are of counts of breeding pairs)


Offloading a team of surveyors on to Boreray
Photograph: Ian Scott

Distant parts of the colony are counted using telescopes
Photograph: Tim Dunn

Further information

Harris, M.P. & Murray, S. 1977. 'Puffins on St Kilda'. British Birds 70: 50-65.

Harris, M.P. & Murray, S. 1989. Birds of St Kilda. Institute of Terrestrial Ecology & Natural Environmental Research Council, UK.

Tasker, M.L., Moore, P.R. & Schofield, R.A. 1987. 'The seabirds of St Kilda'. Scottish Birds 15: 21-29 .

Wanless, S. & Murray, S. 1996. 'A census of the St Kilda Gannetry in May 1994'. Scottish Birds 18(3): 152-158.

 

Joint Nature Conservation Committee
Seabirds & Cetaceans
Dunnet House
7 Thistle Place
Aberdeen AB10 1UZ
UK

Tel: (+44) 01224 655704
URL: www.jncc.gov.uk


© The National Trust for Scotland