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Williamson's sapsucker (Sphyrapicus thyroideus) COSEWIC assessment and status report: chapter 11

Technical Summary

Sphyrapicus thyroideus

Williamson’s Sapsucker: Pic de Williamson

Range of Occurrence in Canada:
British Columbia

Extent and Area Information

Extent of occurrence (EO) (km²)
Developed from published and unpublished data sources (see Distribution section of Report).
43058 km²
Specify trend in EO:
Increased historically, now stable
Are there extreme fluctuations in EO?
No
Area of occupancy (AO) (km²)
Based on known habitat use around currently used locations, primarily based on Gyug (unpublished data) and on other published and unpublished sources (see Distribution section of Report), and on 500-m radius to define habitat use around locations with a single known breeding site (not necessarily currently occupied), and an assumption of the existence of undiscovered nest sites outside known Areas of Occupancy that were included in the Total Population estimate.
1016 km²
Specify trend in AO:
Unknown, probably decreasing
Are there extreme fluctuations in AO?
No
Number of known or inferred current locations:
23 locations
22 S. t. thyroideus
1 S. t. nataliae
Specify trend in # :
Unknown
Are there extreme fluctuations in number of locations?
No
Specify trend in area, extent or quality of habitat :
Decreasing from timber harvesting and land clearing

Population Information

Generation time (average age of parents in the population):
Unknown (minimum of one year to first reproduction)
Number of mature individuals:
Estimated 430
Total population trend:
Decreasing

% decline over the last/next 10 years or 3 generations.

Habitat loss estimated for Okanagan-Greenwood population Area of Occupancy, which represents about 85% of the Total Population numbers. Habitat loss estimated at 23% in last 10 years due to timber harvest, and at up to 53% in the next 10 years based on projected timber harvest.

Are there extreme fluctuations in number of mature individuals?
No
Is the total population severely fragmented?
?
Specify trend in number of populations :
Increasing historically from 1950 to 1970 but stable since then.
Are there extreme fluctuations in number of populations?
No

List populations with number of mature individuals in each: 

Threats (actual or imminent threats to populations or habitats)

Habitat Loss from land clearing and timber harvesting. 

Rescue Effect (immigration from an outside source)

Status of outside population(s)?

USA:
Arizona (S4), California (S3), Colorado (S4B), Idaho (S5B), Montana (S4B), Nevada (S5), New Mexico (S5B,S5N), Oregon (S4B,S3N), Texas (S2N), Utah (S2B), Washington (S4B), Wyoming (S3B).
Is immigration known or possible?
Yes
Would immigrants be adapted to survive in Canada?
Yes
Is there sufficient habitat for immigrants in Canada?
No, main threat is habitat loss
Is rescue from outside populations likely?
No

Quantitative Analysis

Not determined

Current Status

Status and Reasons for Designation

Status: Endangered

Alpha-numeric code: A4c, C1

Reasons for Designation: This woodpecker is associated with mature western larch forests in south-central British Columbia.  Less than 500 adults breed in Canada. Habitat loss through forest harvest is estimated to have been 23%over the last 10 years and is projected to be about 53% over the next decade. 

Applicability of Criteria

Criterion A (Declining Total Population): Endangered A4c

Criterion B (Small Distribution, and De cline or Fluctuation):  Threatened B2abiii if one considers the population fragmented (otherwise does not meet criterion)

Criterion C (Small Total Population Size and Decline): Endangered C1

Criterion D (Very Small Population or Restricted Distribution): Threatened D1

Criterion E (Quantitative Analysis): Not done

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