Golden-winged warbler (Vermivora chrysoptera) COSEWIC assessment and status report: chapter 11

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Technical summary

Vermivora chrysoptera
Golden-winged Warbler     Paruline à ailes dorées
Range of Occurrence in Canada: Manitoba, Ontario, Québec

Extent and Area Information

·        Extent of occurrence (EO)(km²)     Ca. 475,000 km²
               BBS data – area of land covered, where species found.
·        Specify trend in EO     Increasing?
·        Are there extreme fluctuations in EO?     No
·        Area of occupancy (AO) (km²)     Ca. 200-500 km²
               PIF estimates of breeding pairs in Canada multiplied by maximum territory size of 2 hectares per pair.
·        Specify trend in AO     Possibly decreasing.
·        Are there extreme fluctuations in AO?      No.
·        Number of known or inferred current locations     Not applicable
·        Specify trend in #     Not applicable
·        Are there extreme fluctuations in number of locations?     No
·        Specify trend in area, extent or quality of habitat     Likely decreasing.

Population Information

·        Generation time (average age of parents in the population)     2 – 3 years
·        Number of mature individuals     20,000-50,000
·        Total population trend:     Declining
·        % decline over the last/next 10 years or 3 generations.     Ca. 79% over 10 years
BBS data 1993-2002, annual decline of 14.4%
·        Are there extreme fluctuations in number of mature individuals?     No
·        Is the total population severely fragmented?     No
·        Specify trend in number of populations     Not applicable
·        Are there extreme fluctuations in number of populations?     Not applicable
·        List populations with number of mature individuals in each:

Threats (actual or imminent threats to populations or habitats)

Threats to the species are still unresolved but likely include:
-   hybridization with Blue-winged Warblers (V. pinus)
-   habitat loss on the breeding and wintering grounds
-   parasitism by Brown-headed Cowbirds (Molothrus ater)

Rescue Effect (immigration from an outside source)

·        Status of outside population(s)?
·        USA – Large but declining.
·        Is immigration known or possible?     Likely
·        Would immigrants be adapted to survive in Canada?     Yes
·        Is there sufficient habitat for immigrants in Canada?     Yes
·        Is rescue from outside populations likely?     Unknown

Quantitative Analysis     None available

Current Status
COSEWIC: Threatened ( 2006)

Status and Reasons for Designation

Status:  Threatened
Alpha-numeric code: Met criterion for Endangered, A2be, but designated Threatened because the species is still widespread, shows the ability to maintain small pure populations within the Blue-winged Warbler range, is still expanding in Manitoba, and is thus not in imminent danger of extinction. Criterion met for Threatened: A2be.
Reasons for Designation: This small songbird has declined by 79% over the last 10 years according to Breeding Bird Survey data from Canada. The main threat appears to be competition and genetic swamping (hybridization) from the closely related Blue-winged Warbler, which is spreading north because of habitat change and perhaps climate change.

Applicability of Criteria

Criterion A: (Declining Total Population):  Met Endangered A2be, through Breeding Bird Survey results, which indicate a 79% decline between 1993 and 2002.
Criterion B: (Small Distribution, and Decline or Fluctuation):  not applicable
Criterion C: (Small Total Population Size and Decline): not applicable
Criterion D: (Very Small Population or Restricted Distribution): not applicable
Criterion E: (Quantitative Analysis): not available.