Population status

Cory's Shearwater
(Calonectris diomedea)

At-sea surveys conducted between 1965 and 1992 suggest that low numbers of Cory’s Shearwater occur regularly in Canadian waters (Brown 1986). More recent surveys conducted since 2006 show Cory’s Shearwater densities have increased in the waters off Nova Scotia in particular (Gjerdrum et al. 2018). This increase in detections at sea is likely the result of a redistribution of birds onto the Scotian Shelf (Gjerdrum et al. 2018). The quality of data for the global population is generally poor, but historical records from the world’s largest breeding colony (Selvagem Grande in the Portuguese Madeira archipelago) indicate a significant decline from an estimated 140,000 breeding pairs in the early 1900s, to 7,000 following an intense harvest of chicks and adults for meat, oil, and feathers in 1975 and 1976 (Granadeiro et al. 2006). Following this decline, enforced protection began and census work from 1980 to 2005 suggests sustained growth of about 4.6% per year over this time period (Granadeiro et al. 2006). Though data from Canada suggest a recent increase in the density of birds using Canadian waters, there are insufficient data dating back to 1970 to allow for a population assessment relative to that time period. A national population goal for Cory’s Shearwater has therefore not yet been determined.

 

Population goal and acceptable levels of variation

Species/groupGoalLower levelUpper level
Cory's ShearwaterTo be determinedTo be determinedNot applicable

References