Storm Petrel – 2003-07 breeding

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

Comparison with previous atlas:

1984-882003-07
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

Storm Petrel – 1994

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

1984-88
Breeding confirmed3
Breeding probable
Breeding possible
No of tetrads occupied3 (of 478)
Percentage of tetrads0.6%

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.

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

DAVIS, P.E. 1957. The breeding of the Storm Petrel. British Birds 50: 85-101, 371-374.

LOCKLEY, R.M. 1932. On the breeding habits of the Storm Petrel with special reference to its incubation and fledging periods. British Birds 25: 206—211.

SCOTT, D, 1970. The breeding biology of the Storm Petrel. PhD Thesis, University of Oxford.

More about the Storm Petrel in Pembrokeshire

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

More about the Storm Petrel in Pembrokeshire

Storm Petrel – 1894

Procellaria pelagica

This, tiny Petrel, commonly known by the name of ” Mother Carey’s Chicken,” is resident on Skomer Island, where it nests in the chinks of an old wall on the top of the cliff, and probably nests also on other islands off the Pembrokeshire coast. When we were on Skomer on the last day of May we visited this wall, but as the Storm-Petrels are late in breeding there were no eggs there then, although we distinctly perceived the unmistakable Petrel odour clinging in places to the stones, showing that the birds were at that time visiting the wall.

The Storm Petrel does not lay its single white egg before the end of June, or even later, for in the Zoologist for 1886, p. 457, the Rev. H. A. Macpherson mentions an adult and nestling that he saw in Leadenhall market, in London, as late as 20th September. Both, he was told, had come from Skomer ; the nestling was taken on 18th September, and was fully feathered, but still retained some of the sooty down, especially upon the belly.

After severe gales the little Storm Petrel is occasionally picked up inland at some distance from the coast. In stormy weather in the autumn some are captured at the Light House on the South Bishop’s Rock; on the night of October 14, 1883, eight were taken; it was misty weather, with a S.E. breeze, and a drizzling rain. A great number of small birds struck that night against the light, ninety were killed, and two hundred were taken in a net. Three “Falcon Hawks and a Large-horned Owl” were also present, and “made sad havoc among them” (Migration Reports, 1883).

It seems strange that the Storm Petrels should be betrayed into danger by the glare of the Light House lights. One would have thought that, from being always about and skimming over the water at night time, they would have become accustomed to the lights; we can only suppose that in misty weather they are bewildered and become reckless, and so approach too near to what in ordinary weather they would be careful to avoid.

Mathew M.A. 1894, Birds of Pembrokeshire and its Islands

More about the Storm Petrel in Pembrokeshire

Storm Petrel

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

Storm Petrel – 2003-07 breeding

Hydrobates pelagicus – PEDRYN DRYCIN – Breeding summer visitor. Not recorded in January and February. Comparison with previous atlas: 1984-88 2003-07 Breeding confirmed 3 3 Breeding probable Breeding possible No of tetrads occupied 3 (of 478) 3 (of 490) Percentage of tetrads <1% <1% Storm Petrels breed only on the offshore islands, preferring rocky scree […]

Storm Petrel – 1994

Hydrobates pelagicus – PEDRYN DRYCIN – Breeding summer visitor. Not recorded in January and February. 1984-88 Breeding confirmed 3 Breeding probable Breeding possible No of tetrads occupied 3 (of 478) Percentage of tetrads 0.6% Storm Petrels are difficult birds to survey, since they nest in crevices, often on inaccessible scree slopes. However, 6,000 pairs were […]

Storm Petrel – 1949

Species account from the Birds of Pembrokeshire, 1949, by Lockley, Ingram and Salmon.

Storm Petrel – 1894

Procellaria pelagica This, tiny Petrel, commonly known by the name of ” Mother Carey’s Chicken,” is resident on Skomer Island, where it nests in the chinks of an old wall on the top of the cliff, and probably nests also on other islands off the Pembrokeshire coast. When we were on Skomer on the last day of May we visited […]