Canada warbler COSEWIC assessment and status report: chapter 11

Technical Summary

Wilsonia canadensis

Canada Warbler – Paruline du Canada

Range of Occurrence in Canada:

Yukon, Northwest Territories, British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island

Extent and Area Information

Extent of occurrence (EO) (km²):
2,200,000 km²
Specify trend in EO:
Are there extreme fluctuations in EO?
Area of occupancy (AO) (km²)
home range of 2 ha (Chase 2005) * 1.35 million breeding pairs (see Abundance section for estimate of population size): 27,000 km²
Specify trend in AO:
Are there extreme fluctuations in AO?
Number of current locations:
Specify trend in #:
Are there extreme fluctuations in number of locations?
Specify trend in area, extent or quality of habitat:

Population Information

Generation time (average age of parents in the population):
2–3 years
Number of mature individuals
(see Abundance section for estimate of population size): approximately 2.7 million
Total population trend:
% decline over the last/next 10 years or 3 generations
based on BBS trends between 1997 and 2007: 43%
Are there extreme fluctuations in number of mature individuals?
Is the total population severely fragmented?
Specify trend in number of populations:
Are there extreme fluctuations in number of populations?
List populations with number of mature individuals in each:

Threats (actual or imminent threats to populations or habitats)

  • Habitat loss in wintering grounds due to clearing of primary mountain forest
  • Habitat loss/degradation in breeding grounds due to clearing for agriculture, urban development and road development

Rescue Effect (immigration from an outside source)

Status of outside population(s)?
USA: significant decline of 1.8%/year (1966–2006); Imperiled in the following states: Illinois, Indiana, Ohio
Is immigration known or possible?
Would immigrants be adapted to survive in Canada?
Is there sufficient habitat for immigrants in Canada?
Is rescue from outside populations likely?
Limited given declines in U.S.

Quantitative Analysis


Current Status

COSEWIC: Threatened (April 2008)

Status and Reasons for Designation

Status: Threatened

Alpha-numeric code: A2b

Reasons for Designation: Most (80%) of the breeding range of this species occurs in Canada. While regional trends may vary, overall the species has experienced a significant long-term decline. This decline is particularly evident in the case of the species’ Canadian range and there is no indication that this trend will be reversed. The reasons for the decline are unclear, but loss of primary forest on the wintering grounds in South America is a potential cause.

Applicability of Criteria

  • Criterion A: (Declining Total Population):Meets criterion A2b, with a reduction in population size of > 30% in the last three generations, based on an appropriate index of abundance.
  • Criterion B: (Small Distribution, and Decline or Fluctuation): Not applicable - Extent of Occurrence > 20,000 km² and Area of Occupancy > 2,000 km².
  • Criterion C: (Small Total Population Size and Decline):Not applicable - total population size > than 10,000.
  • Criterion D: (Very Small Population or Restricted Distribution): Not applicable - population size > than 1,000 and Area of Occupancy > than 20 km².
  • Criterion E: (Quantitative Analysis): Not applicable.
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