Leach's Storm-petrel Oceanodroma leucorhoa

Status;  International importance;  Population estimates;  Distribution;  Annual abundance/ productivity; Phenology/diet/survival

 

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Description

Leach's Storm-petrel vignette

The following has been adapted from original text by P. Ian Mitchell in Seabird Populations of Britain and Ireland (with permission from A&C Black, London).

 

Leach's storm-petrel is a truly oceanic species, only returning to remote island colonies during hours of darkness. It ranges widely in both the Atlantic and Pacific Oceans. In the east Atlantic, breeding colonies are confined to a few islands off the coasts of Iceland, the Faeroes and Norway, as well as just eight remote islands and archipelagos situated along the Atlantic Frontier of Britain and Ireland. Obtaining estimates of breeding numbers has been virtually impossible in the past, due to the species' nocturnal and subterranean breeding habits plus accessing the remote colonies during the hours of darkness is often difficult and dangerous.


Conservation status

 

Leach's storm-petrel is currently identified as a conservation priority in the following:

Amber listed in Birds of Conservation Concern 4 (2015 update)

Wildlife and Countryside Act 1981 - protected under Schedule 1

EC Birds Directive - e.g. listed in Annex 1 and as a migratory species

(further information on Conservation Designations for UK Taxa)

Red listed in  Birds of Conservation Concern in Ireland 2014-2019 (2014 update)


International importance

 

UK Population % Biogeographic Population % World Population
48,000 AOS* 0.9 (ssp. leucorhoa) 0.5

 

* AOS = Apparently Occupied Sites

The UK population figure (rounded to the nearest hundred) was derived from data in Mitchell, P.I., Newton, S.F., Ratcliffe, N. and Dunn, T.E. (eds.) 2004. Seabird Populations of Britain and Ireland. Poyser, London. This was also the source of figures for the Biogeographic and World populations.

 


UK population estimates and change 1969-2002 (census data)

 

Seabird 2000 used a method called tape-playback to survey apparently occupied sites (AOS) of breeding Leach's storm-petrels. The method involves playing calls of the species to elicit a response from adults hidden in burrows during the day whilst incubating. Unfortunately, not all Leach's storm-petrels present at a colony will respond to the taped calls; thus counts of responses will underestimate the number of AOS and have to be adjusted by a response rate measured at the colony.

 

Ninety-four percent of the UK population breeds on four islands in the St Kilda archipelago (Western Isles), with the remainder on the Flannan Isles (Western Isles), three other islands in the Western Isles and two islands in Shetland. There is also one Irish colony. Colonisation of islands by Leach's storm-petrels is dependent on the absence of mammalian predators and on proximity to their feeding grounds. The species feeds on macro-zooplankton (e.g. myctophids, amphipods, euphausiids) and during the east Atlantic breeding season is confined to feeding in areas beyond the continental shelf break (deeper than 200m). All Leach's storm-petrel colonies are within 37-67km of the shelf break and 65-119km from the bottom of the continental slope (200m-1000m).

 

 

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

UK Population estimate (AOS*) N/a N/a 48,047
% change since previous census N/a N/a n/a

 

* AOS = Apparently Occupied Sites

For census results for individual countries and Ireland, the Channel Islands and the Isle of Man see under relevant sections below.

 


Distribution/abundance

 

The Seabird 2000 census provides the most comprehensive recent assessment of the distribution and abundance of breeding seabirds. Numbers of Leach's storm-petrel found in different regions, and a map showing the location and size of colonies, is provided in the Seabird 2000 Leach's storm-petrel results page (PDF,  1.2 mb).

 

An interactive map is available on the NBN Gateway, where you can filter to display only the Seabird 2000 data.  For more recent, but less comprehensive, coverage view the distribution on the NBN with all available contributing datasets.

 

The locations sampled during the annual Seabird Monitoring Programme provide some information on distribution and are accessible via the Seabird Monitoring Programme online database.

 

Annual abundance and productivity by geographical area

 

With reference to the regional accounts below please note the following.

Breeding abundance: graphs of abundance index with 95% CLs are only shown for a region where the trend produced has been deemed accurate (see methods of analysis). Where a trend was thought to be inaccurate, graphs of abundance at major colonies in a region may be shown instead, particularly if such colonies hold greater than 10% of the regional population, are monitored frequently and may thus help illustrate regional population fluctuations outwith national censuses. Occasionally, too few data have been collected regionally to produce either of these.

Productivity: graphs of productivity are only shown if analysis of breeding success data produced a significant result for regional and/or year effects (again see methods of analysis). If results were not significant, then a regional mean productivity value is given. However, on some occasions too few data are available from which to provide a meaningful average. Furthermore, for 11 species where the quality of monitoring data available was considered high, population viability analysis was undertaken at the UK level and the results of this are also reported.   

 



 

Breeding abundance

 

The first comprehensive estimates of population size of Leach’s storm-petrel were obtained during the Seabird 2000 Census, when 48,000 pairs were counted. Due to the logistical difficulty in monitoring this nocturnal and burrow-nesting species, little information exists as to population trends. However, repeat surveys of the largest colony in the UK, on Dun in the St Kilda archipelago, which at the last census held around 58% of the UK population, have shown a decline. Surveys showed that the population here fell from 27,800 AOS in 1999 to 14,500 in 2003, with a repeat survey in 2006 estimating 12,800 AOS1. A decline has also recently been found on North Rona (Western Isles), where 1,084 AOS were estimated in 2001. A repeat survey there in 2009 estimated the population at 713 AOS – a fall of 34%2. The causes of both these declines are not known, though predation at breeding colonies by great skua Stercorarius skua and great black-backed gulls Larus marinus has been advanced as a possible cause. On St Kilda, it was estimated that great skuas can consume as many as 21,000 individual Leach's storm-petrels per year3, predominantly non-breeding individuals, which could subsequently impact on the size of the colony through reduced recruitment. Other causes of decline include reduced adult survival or a decrease in food supply during chick rearing, but no information is currently available on these last two factors. In Shetland, where small numbers of Leach's storm-petrel nest, tape-playback surveys of 10 islands in 2011 found the species only on two isles; 13 responses were recorded on Gruney with a single responding bird on Gloup Holm. Examination of four burrows from which birds had responded on Gruney found that two actually contained non-breeders. While sample sizes here are very small, burrow occupancy by non-breeders is unexpected and further work is required to determine the extent of this behaviour as it has potential implications for the interpretation of Leach's storm-petrel population estimates derived from tape-playback surveys4

 

Productivity

 

Within the UK this species breeds only in Scotland. Data submitted to the SMP on the productivity of Leach's storm-petrels at Scottish colonies is sparse; thus, no meaningful average productivity value can be given.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AOS*) N/a N/a 48,047
% change since previous census    N/a N/a N/a

 

* AOS = Apparently Occupied Sites

 

Breeding Abundance

 

The first comprehensive estimates of population size of Leach’s storm-petrel were obtained during the Seabird 2000 Census, when 48,000 pairs were counted. Due to the logistical difficulty in monitoring this nocturnal and burrow-nesting species, little information exists as to population trends. However, repeat surveys of the largest colony in the UK, on Dun in the St Kilda archipelago, which at the last census held around 58% of the UK population, have shown a decline. Surveys showed that the population here fell from 27,800 AOS in 1999 to 14,500 in 2003, with a repeat survey in 2006 estimating 12,800 AOS1. A decline has also been found on North Rona (Western Isles), where 1,084 AOS were estimated in 2001. A repeat survey there in 2009 estimated the population at 713 AOS – a fall of 34%2. The causes of both these declines are not known, though predation at breeding colonies by great skua Stercorarius skua and great black-backed gulls Larus marinus has been advanced as a possible cause. On St Kilda, it was estimated that great skuas can consume as many as 21,000 individual Leach's storm-petrels per year3, predominantly non-breeders, which could subsequently impact on the size of the colony through reduced recruitment. Other causes of decline include reduced adult survival or a decrease in food supply during chick rearing, but no information is currently available on these last two factors. In Shetland, where small numbers of Leach's storm-petrel nest, tape-playback surveys of 10 islands in 2011 found the species only on two isles; 13 responses were recorded on Gruney with a single responding bird on Gloup Holm. Examination of four burrows from which birds had responded on Gruney found that two actually contained non-breeders. While sample sizes here are very small, burrow occupancy by non-breeders is unexpected and further work is required to determine the extent of this behaviour as it has potential implications for the interpretation of Leach's storm-petrel population estimates derived from tape-playback surveys4. Due to the logistical difficulty in monitoring this nocturnal and burrow-nesting species, no information exists as to population trends and no sizable colonies have been re-surveyed since Seabird 2000.

 

Productivity

 

Data submitted to the SMP on the productivity of Leach's storm-petrels in Scotland are sparse; thus, no meaningful average productivity value can be given.

 

 

Leach's storm-petrel does not breed in England.

 

 

Leach's storm-petrel does not breed in Wales.

 

 

Leach's storm-petrel does not breed in Northern Ireland.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AOS*) N/a N/a 310
% change since previous census    N/a N/a N/a

 

* AOS = Apparently Occupied Sites

 

Breeding Abundance

 

The first comprehensive estimates of the population size of Leach’s storm-petrel for the Republic of Ireland were obtained during the Seabird 2000 Census. Only one colony was found, on the Stags of Broadhaven in County Mayo which held 310 AOS. Two other suspected colonies, on Great Skellig (Co. Kerry) and Inishglora (also Co. Mayo), were also surveyed but no Leach's storm-petrels were found nesting. In 2015, Great Skellig (Co. Kerry) was surveyed but no Leach's storm-petrels were found nesting5.

 

Productivity

 

No systematic data on the productivity of Leach's storm-petrels in the Republic of Ireland have been submitted to the SMP.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AOS*) N/a N/a 310
% change since previous census    N/a N/a N/a

 

* AOS = Apparently Occupied Sites

 

Breeding Abundance

 

Within Ireland, the Leach's storm-petrel nests only in the Republic of Ireland. Thus, all data and text for the Republic of Ireland is also pertinent to the status of the species for the whole of Ireland.

 

Productivity

 

This species does not breed in Northern Ireland and no systematic data on the productivity of Leach's storm-petrels in the Republic of Ireland have been submitted to the SMP.

 

 

Leach's storm-petrel does not breed on the Isle of Man.

 

 

Leach's storm-petrel does not breed on the Channel Islands.

 

 


UK phenology, diet, survival rates

 

No data have been collected as part of the Seabird Monitoring Programme.

 


References

1 Newson, S.E., Mitchell, P.I., Parsons, M., O’Brien, S.H., Austin, G.E., Benn, S., Black, J., Blackburn, J. Brodie, B., Humphreys, E., Prior, M. and Webster, M. 2008. Population decline of Leach’s Storm-petrel Oceanodroma leucorhoa within the largest colony in Britain and Ireland. Seabird 21: 77-84.

2 Murray, S., Shewry, M.C., Harden, J., Jamie, K. and Parsons, M. 2010. A survey of Leach's Oceanodroma leucorhoa and European Storm-petrel Hydrobates pelagicus populations on North Rona and Sula Sgeir, Western Isles, Scotland, in 2009. Seabird 23: 25-40.

3 Miles, W.T.S. 2010. Ecology, behaviour and predatorprey interactions of Great Skuas and Leach's Storm-petrels at St Kilda. Unpublished PhD thesis http://theses.gla.ac.uk/2297/. University of Glasgow, Glasgow.

4 Miles, W.T.S., Tallack, R.M., Harvey, P.V., Ellis, P.M., Riddington, R.,  Tyler, G., Gear, S.C., Okill, J.D., Brown, J.G., and Harper, N. 2012. A survey of Leach's petrels on Shetland in 2011. Scottish Birds 32: 22-29.

5 Newton, S.  Lewis, L. and  Trewby, M. 2015. Results of a Breeding Survey of Important Cliff‐Nesting Seabird Colonies in Ireland 2015. National Parks and Wildlife Service Ireland.

 


Partners

Data have been provided to the SMP by the generous contributions of its partners, other organisations and volunteers throughout Britain and Ireland. Partners to the SMP are: BirdWatch Ireland; The British Trust for Ornithology; Centre for Ecology and Hydrology; Natural Resources Wales; Department of Environment, Food and Agriculture (Isle of Man); Department of Environment, Heritage and Local Government (Republic of Ireland); States of Guernsey Government; JNCC; Manx Birdlife; Manx National Heritage; The National Trust; National Trust for Scotland; Natural England; Northern Ireland Environment Agency; The Royal Society for the Protection of Birds; Scottish Natural Heritage; Seabird Group; Shetland Oil Terminal Environmental Advisory Group; Scottish Wildlife Trust.  More about the SMP partners >>

 
Image of Leach's storm-petrel appears courtesy of Ian Rendall ©, is subject to international copyright law and may not be reproduced in any form whatsoever.