Justification of Red List Category
Although the trend of western North American and Russian populations are unknown, the compilation of available data collected from 1977 to 2016 representing 75-80% of the global population, points to a decline of ≥30% over three generations. It has therefore been uplisted to Vulnerable. The cause(s) of declines are unknown, but are likely multi-faceted and further research is needed to inform conservation actions.
Brooke (2004) estimated the global population to number > c.20,000,000 individuals. Based on the compilation of available data the current population comprises 6.7-8.3 million breeding pairs; 40-48% of these breed in the Atlantic basin and 52-60% in the Pacific. Throughout the western Atlantic (>90% of basin total), populations are declining, including at Baccalieu Island, Newfoundland, Canada, the site of the species largest colony. The population at Baccalieu Island, estimated at 3.3 million breeding pairs in 1984 (Sklepkovych and Montevecchi 1989), had declined to 2.02 million pairs by 2013 (Environment Canada, unpublished data), and the former second and third regionally largest colonies have declined by >50% since the late 1990s (Wilhelm et al. 2015; Environment Canada, unpublished data). In the eastern Atlantic, the population at St. Kilda is also declining, this being the largest colony in the UK and Ireland (Newson et al. 2008). Population trends in the Pacific are less well known. In Alaska, where Leach’s and Fork-tailed Storm-petrels are largely combined for monitoring purposes, population trends are stable or increasing (Slater and Byrd 2009; Dragoo et al. 2015), the large population at Daikoku Island, Japan may have declined since 1982, while trends of western North American and Russian populations are unknown. Despite these knowledge gaps, compiling available data collected between 1977 and 2016, representing 75-80% of the global population (including Europe, eastern North America, and Japan), points to a decline of ≥30% over three generations (39 years, based on a generation length estimated by BirdLife to be 13 years).
Definitive information on Leach’s Storm-petrel population decline comes mainly from colonies within the Atlantic basin. Recent genetics research indicates that while there is no genetic structure among Atlantic colonies, that populations within the Atlantic and the Pacific are genetically distinct (Bicknell et al. 2012). Evidence of movement of pre-breeding birds among colonies within the Atlantic, led Bicknell et al. (2014) to conclude that North Atlantic birds may be operating as a metapopulation and that management of this species may be best viewed at an oceanic scale (Bicknell et al. 2012).
Data collected from 1977 to 2016 representing 75-80% of the global population, points to a decline of ≥30% over three generations. The cause(s) of declines are unknown, but are likely multi-faceted and further research is needed to inform conservation actions.
This species has an extensive global range. Breeding colonies are largely confined to the northern hemisphere, from the South Kuril Islands (Japan) round to Baja California (Mexico) including the Aleutian Islands, Alaska (USA) and Canada in the Pacific, and in the north-east North America, Iceland, northern United Kingdom and Norway in the Atlantic. Small numbers also breed off South Africa (Underhill et al. 2002). Northern populations migration south into the tropics in winter, reaching the equator in the Pacific and as far south as south Brazil and South Africa in the Atlantic (del Hoyo et al. 1992). Subspecies in Baja California (Mexico) may be separate species.
This species is marine and pelagic, often occurring in areas of convergence or upwelling or over continental shelves, rarely coming near land except at colonies. During the breeding season, birds from the western Atlantic are highly pelagic in their foraging habits, travelling to deep (median > 1,950 m) and relatively unproductive waters (chlorophyll a concentrations < 0.5 mg/m3) over and beyond continental slopes lying, on average, 400 to 830 km from colonies (Pollet et al. 2014; Hedd et al. in revision). Its diet comprises mainly of small fish, squid, planktonic crustaceans and offal which it catches on the wing by dipping, skimming or snatching from the surface. It sometimes follows marine mammals feeding on leftovers or faeces. Its breeding season is variable depending on locality, forming colonies on offshore islands on high ground or slopes, usually among rocks but also in soft soil between trees (del Hoyo et al. 1992).
The cause(s) of population decline are unknown, but are likely multi-faceted. Heavy predation by seabirds and mammals occurs at some declining colonies in the eastern and western Atlantic (Phillips et al. 1997, 1999; Stenhouse et al. 2000; Votier et al. 2006). In the western Atlantic, large gulls (Larus spp.; Stenhouse et al. 2000; Robertson et al. 2006) and mammals (e.g., mink Neovison vison, and meadow voles Microtus pennsylvanicus) prey upon adults, eggs and chicks. At Great Island, Newfoundland, Canada, gulls were estimated to have killed 49,000 storm-petrels in 1997 alone (Stenhouse et al. 2000). Within Europe, the species suffers severe predation, chiefly by native species including gulls (e.g. Herring [L. argentatus], Great Black-backed [L. marinus] and Lesser Black-backed Gulls [L. fuscus]), Great Skuas (Catharacta skua), as well as from introduced mammalian predators; rats (Rattus spp.), cats (Felis catus), mice (Mus musculus), mink, otters and foxes; these are responsible for some local declines, and some colonies having moved to predator-free offshore stacks (Carboneras et al. 2014). In the western Atlantic, mercury concentrations in the tissues of Leach’s Storm-petrels are high relative to other seabirds in the region (Elliott et al. 1992; Bond and Diamond 2009). Studies investigating regional differences in contaminant burdens and their associations with diets and foraging patterns are currently under way (Burgess et al. 2014; Hedd et al. 2016). Annual adult survival rates are low (77-85%) at colonies throughout the western Atlantic, and are likely a key demographic driver of observed declines (Fife et al. 2015; Hedd et al. 2016). High reproductive success at the centre of the western Atlantic breeding range indicates favourable summer food supply (Hedd et al. unpublished data), however, low body mass of adults on return to the colony in years with poor survival suggests potential carryover effects. Influences of ocean climate variation and change on food supply in winter are unknown but require investigation. As a result of their attraction to light, Leach’s Storm-petrels are also vulnerable to collision and stranding both onshore and offshore. In the offshore, risks include attraction/collision with vessels and with lights and flares at oil and gas production platforms. Secondarily they include hydrocarbon contamination from operational discharges and spills (Burke et al. 2012; Ellis et al. 2013; Fraser 2014). Foraging ranges during the breeding season for 4 of 7 western Atlantic colonies overlapped with offshore oil and gas operations; 3 of these colonies have declined in recent decades (Pollet et al. 2014; Hedd et al. 2016; Hedd et al. in revision). More information on avian attraction and interaction with vessels and platforms is needed throughout the breeding and nonbreeding range to assess potential significance. Leach’s Storm-petrel may also be vulnerable to collisions with wind farms, although the current risk to the population is assessed as low (Bradbury et al. 2014).
Conservation Actions Underway
It is listed in Appendix II of the Bern Convention, and Annex I of the EU Birds Directive. The following information refers to the species European range only: it is listed as occurring in nine marine Important Bird Areas in Europe, with sites in Iceland, Ireland and the United Kingdom. In the EU it is listed within 25 Special Protection Areas in France, Ireland, Spain and the United Kingdom. Various countries, including the United Kingdom have introduced artificial nest boxes to breeding colonies to reduce the predation risk and to facilitate monitoring of breeding success (Newson et al. 2008).
Conservation Actions Proposed
Estimates of population size and trend are needed in Europe, western North America, Alaska and Russia. All large breeding colonies in Canada are protected under provincial and/or federal protected area legislation. Additionally, all major Canadian colonies are Important Bird Areas (http://www.ibacanada.ca/). Continued monitoring of adult survival and breeding success are needed at colonies in the western Atlantic and additional information about the threats currently affecting this species is needed across its range.
The following information refers to the species' European range only: continued monitoring of breeding success at colonies, including the provision of artificial nest boxes. Management of invasive predators.
Text account compilers
Ashpole, J, Butchart, S., Calvert, R., Ekstrom, J. & Moreno, R.
Bond, A. & Hedd, A.
BirdLife International (2018) Species factsheet: Hydrobates leucorhous. Downloaded from http://www.birdlife.org on 26/09/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/09/2018.