Storm Petrel – 2003-07 breeding

Hydrobates pelagicus – PEDRYN DRYCIN – Breeding summer visitor. Not recorded in January and February.

Comparison with previous atlas:

Breeding confirmed33
Breeding probable
Breeding possible
No of tetrads occupied3 (of 478)3 (of 490)
Percentage of tetrads<1%<1%

Storm Petrels breed only on the offshore islands, preferring rocky scree slopes and boulder areas where they can find small crevices and burrows to nest in. Sometimes you can smell their slightly fishy odour near their nest chamber but the best clue that they are present is their soft purring and clicky song. On Skokholm they nest in the herringbone style walls, in the boulder scree in the bays and especially in the “quarry” – a large boulder rockfall area on the north western corner of the island.

They are a very difficult species to census and a huge amount of effort has gone into establishing a reliable method of gaining consistent data. Nationally the use of a song playback system, listening for responses from the birds to taped calls played to the burrows, has now been adopted but there are still questions over interpretation of the results.  In consequence the historical data, (pre 1980’s) may not be directly comparable recent census results. Until a consistent methodology is applied, the information available is a “best guess” at a particular time.

In the first decade of the 2000’s,  the best information available suggests populations of up to 100 pairs on Ramsey and North Bishop, perhaps around 150 pairs on Skomer and 2,000 pairs on Skokholm. The estimates on Skomer suggest a recent increase although this may mainly relate to new sites being located.  On Skokholm the population has certainly declined as many known nest sites in the wall systems have been deserted. The latest census attempt in 2003 estimated the population to be only 1,011 apparently occupied sites on the whole island, compared with varying estimates of 5,000 to 7,000 in 1969, 3,000 to 4,000 in 1995 and in 2001 about 2,000 pairs.

There have been no recent studies of Storm Petrels on the Pembrokeshire islands to understand their survival rates or their breeding success, so the reasons for the declines are unknown.

Because of the importance of the Storm Petrel population on the Pembrokeshire Islands (in European and indeed World terms) these island have been designated a Special Protection Area for them (under the EC Directive on the conservation of wild birds (79/409/EEC)

Steve Sutcliffe.

Records extracted from the Pembrokeshire Bird Reports, which may contain more detail than shown here.

More about the Storm Petrel in Pembrokeshire