Storm Petrel - 1949

Hydrobates pelagicus

Mathew knew only of a small colony "in the chinks of an old wall on top of the cliff" on Skomer.  there are still some on Skomer (about 30 pairs in 1946), but the main colony is on Skokholm, estimated in 1939 at 600 pairs.  It is preyed upon extensively by Little Owls on these islands.  Also breeds on islets in St Brides Bay, but not on Grassholm (1934).  Occurs in winter inland occasionally after gales, eg one Haverfordwest 12 Dec 1939.

R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society

Storm Petrel - 2003-07

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.

Fieldwork 2003-07

Red = breeding confirmed = 3

Total tetrads in which registered = 3

Storm Petrel - 1994

Breeding summer visitor. Not recorded in January and February.

Storm Petrels are difficult birds to survey, since they nest in crevices, often on inaccessible scree slopes. However, 6,000 pairs were estimated as breeding at Skokholm in 1969. A survey carried out at Skokholm using a light amplifier, conducted in 1990, resulted in a distribution of colonies little changed from that of a 1967 survey. Recent work at Skomer suggests probably less than 200 pairs breed on that island. Three nests were found on North Bishop in 1985 but it was suspected that there were more. Breeding birds were established on the Green Scar in 1928 and 1930, were probably breeding on Middleholm and have been seen in suitable terrain at St Margaret's Island and on Stack Rocks in St Bride's Bay in the past. It is possible they nest in scree at the foot of some mainland cliffs where they have been seen leaving crevices in the breeding season.

The imprecision of census results obstructs the detection of population trends. There are no mammalian predators at their known nesting localities but they are predated by gulls, by Little Owls at Skomer and formerly at Skokholm, and they occasionally die from other, sometimes bizarre, causes; for instance, a bird died when it became ensnared in the seed head of lesser burdock at Skokholm.

Much of what is known of the breeding cycle of the Storm Petrel is derived from work carried out at Skokholm, first by Lockley (1932), followed by Davis (1957) and Scott, who was resident from 1966 to 1969 (Scott 1970). They arrive in home waters in April, occasionally in March, and most depart by October. Autumnal gales, particularly in early September, can blow considerable numbers inshore; for example, over 100 were seen at Strumble Head on 3 September 1983. Extensive mist netting and ringing at headlands indicates a strong, regular through passage of non-breeding birds late in the breeding season. The breeding population appears to use the Irish Sea only sparingly as a feeding area, but regularly frequents the Bristol Channel and, even more so, the southern Celtic Deep.

 

Fieldwork 1984-88

Red = breeding confirmed = 3

Total tetrads in which registered = 3 

Donovan J.W. & Rees G.H (1994), Birds of Pembrokeshire

Storm Petrel - 1970s breeding

Red = breeding confirmed

Orange = breeding probable

Yellow = breeding possible

Storm Petrel - 1894

Species account from M Mathew, 1894, "The Birds of Pembrokeshire and its islands"

Click to read more ...