Spotted owl (Caurina subspecies) COSEWIC assessment and status report: chapter 12
Technical Summary
Strix occidentalis caurina
Northern Spotted Owl – Chouette tachetée
Extent and Area Information
3.3% of the British Columbia land area (945,000 km²); based
on analyses by Harestad et al. (2004) and Pierce Lefebvre (2005) :
Population Information
to occur between 2009-2012; based on known ages of known
owls and apparent lack of recent recruitment of young owls :
Threats (actual or imminent threats to populations or habitats)
Very low population making it susceptible to stochastic events. High juvenile mortality and no or little current recruitment of young birds into the population. Habitat degradation and loss through logging and conversion of forests to urban/industrial uses. Habitat also susceptible to wildfires and insect outbreaks. Possibly at northern edge of range in BC and limited by climate. Low annual reproductive potential (pairs do not breed every year, fledge 1-2 young when do breed) but adults are long-lived.
Current low numbers, widely separated sites, fragmented habitat and lack of recruitment suggest extirpation in Canada by 2012.
Rescue Effect (immigration from an outside source)
Quantitative Analysis
Extrapolation from current trends and population figures suggest extirpation by 2012.
Current Status
COSEWIC: Endangered
Designated Endangered in April 1986. Status re-examined and confirmed in April 1999, May 2000, and April 2008.
Status and Reasons for Designation
Status: Endangered
Alpha-numeric code: A2ac; B2ab(i,ii,iii,iv,v); C1+2a(i), D1, E
Reasons for Designation: This owl requires old-growth forests for its survival and has suffered a catastrophic population decline over the past 50 years as habitat is lost and fragmented. With the severely depressed population, an additional threat is the recent arrival of the closely related Barred Owl as a breeding bird in B.C.; this species competes with and hybridizes with the present species. Its historical population of about 500 adult owls in Canada has been reduced to 19, and only 10 of these are in breeding pairs. All adults are old and near the end of their breeding age and there is no recruitment of young owls into the population. If current trends are not reversed, extirpation will likely occur within the next decade.
Applicability of Criteria
Criterion A: (Declining Total Population): Meets Endangered A2ac.
Criterion B: (Small Distribution, and Decline or Fluctuation): Meets Endangered B2ab(i,ii,iii,iv,v)
Criterion C: (Small Total Population Size and Decline): Meets Endangered C1+2a(i)
Criterion D: (Very Small Population or Restricted Distribution): Meets Endangered D1
Criterion E: (Quantitative Analysis): Endangered E (extirpation predicted by 2012)
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