Population status

Sooty Shearwater
(Ardenna grisea)

Pelagic surveys conducted between 1982 and 2005 off the Pacific coast of Canada have recorded Sooty Shearwaters between January and November (Kenyon et al. 2009). Low numbers have also been reported in December off the coast of British Columbia (Campbell et al. 1990a) and Washington (Wahl et al. 2005); thus, it is likely that Sooty Shearwaters are present in Canadian Pacific waters throughout the year. The highest concentrations (April through October) have been observed over the continental shelf and along the shelfbreak (Kenyon et al. 2009). High numbers of Sooty Shearwaters (estimated between 500,000 and 1,000,000) have been reported from Hecate Strait during the spring and early summer (Campbell et al. 1990a). Off the Atlantic coast, pelagic surveys conducted under the Eastern Canada Seabirds at Sea Program (2006-2016) report most frequent observations and highest densities of Sooty Shearwates in summer and fall off both Nova Scotia and Newfoundland and Labrador; with fewer birds being observed in winter and spring (Fifield et al. 2009, Fifield et al. 2016). On average, 400 individuals have been observed annually by these surveys (Fifield et al. 2009, C. Gjerdrum, Environment and Climate Change Canada, unpublished data). Globally, the estimated population of more than 20,000,000 birds has decreased since about 1970 (Brooke 2004). There have been significant declines in their core breeding range in the South Pacific, including at many of the largest New Zealand colonies. For example, at the largest colony in the Snares Islands, the number of burrows counted between 1996 and 2001 decreased by ~37% when compared to the numbers detected between 1969 and 1971 (Scofield 2002). Elsewhere in New Zealand, colonies declined by an estimated 54% between the 1940s and the late 1990s (Jones 2000). There have been significant changes in the at-sea observations of Sooty Shearwaters in the northeastern Pacific. One study found that the number of birds encountered during pelagic surveys off the west coast of the United States from 1987 to 1994 dropped by 90% (Veit et al. 1996). However, it remains unclear whether that short-term decline reflects a global population decrease, or merely a shift in the at-sea distribution in response to changing oceanic conditions (Spear and Ainley 1999). A decline of >30% in the abundance of Sooty Shearwaters between 1985 and 2006 in the central portion of the California current system was also found, though there was high annual variability in the estimate (Ainley and Hyrenbach 2010). These declines are consistent with those at South Pacific breeding colonies (Jones 2000). In contrast, the Sooty Shearwater population is thought to have increased on Kidney Island, Falkland Islands, their largest known breeding colony in the South Atlantic (Falklands Conservation 2006). Sooty Shearwaters have not been sufficiently monitored in Canada to reliably determine a change in population status relative to 1970. As such, a national population goal for the species has not yet been determined.

 

 

Population goal and acceptable levels of variation

Species/groupGoalLower levelUpper level
Sooty ShearwaterTo be determinedTo be determinedNot applicable

References