Rusty blackbird (Euphagus carolinus) COSEWIC assessment and status report: chapter 11

Technical Summary

Euphagus carolinus

Rusty Blackbird – Quiscale rouilleux

Range of occurrence in Canada: Prince Edward Island, Nova Scotia, New Brunswick, Newfoundland and Labrador, Québec, Ontario, Manitoba, Saskatchewan, Alberta, British Columbia, Yukon, NWT and Nunavut

Extent and Area Information

Extent of occurrence (EO) (km²)
70% of the total North American breeding range of 7.6 million km²:
5.3 million km²
Specify trend in EO :
stable
Are there extreme fluctuations in EO?
no
Area of occupancy (AO) (km²) :
unknown, but large
Specify trend in AO :
unknown
Are there extreme fluctuations in AO?
not likely
Number of known or inferred current locations :
not applicable
Specify trend in # :
not applicable
Are there extreme fluctuations in number of locations?
not applicable
Specify trend in area, extent or quality of habitat :
likely stable on breeding grounds, but declining on wintering grounds

Population Information

Generation time (average age of parents in the population) :
2-3 years

Number of mature individuals

  • minimum based on extrapolation of roost counts from 1970s
  • maximum based on Breeding Bird Survey data: 110,400 to 1.4 million
Total population trend:
decline
% decline over the last/next 10 years or 3 generations
Based on Christmas Bird Count data:
- decline of 85% between 1966 and 2003
- decline of 18.3% in last 10 years
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:
not applicable

Threats (actual or imminent threats to populations or habitats)

  • Habitat loss caused by wetland conversion to agricultural land on wintering grounds
  • Some additional localized habitat loss on breeding grounds because of activities such as wetland conversion, creation of hydroelectric reservoirs
  • Bird control programs on wintering grounds

Rescue Effect (immigration from an outside source)

Status of outside population(s)?
USA: Declining
Is immigration known or possible?
yes
Would immigrants be adapted to survive in Canada?
yes
Is there sufficient habitat for immigrants in Canada?
yes
Is rescue from outside populations likely?
limited rescue because most of range is in Canada

Quantitative Analysis

none

Current Status

COSEWIC: Special Concern (2006)

Status and Reasons for Designation

Status: Special Concern

Alpha-numeric code: Not applicable

Reasons for Designation: More than 70% of the breeding range of this species is in Canada’s boreal forest.  The species has experienced a severe decline that appears to be ongoing, albeit at a slower rate.  There is no evidence to suggest that this trend will be reversed.  Known threats occur primarily on the winter range in the United States, and include habitat conversion and blackbird control programs.

Applicability of Criteria

Criterion A: (Declining Total Population): Does not meet criterion - population decline < 30%.

Criterion B: (Small Distribution and Decline or Fluctuation): Does not meet criterion - Extent of Occurrence > 20,000 km² and Area of Occupancy > 2,000 km².

Criterion C (Small Total Population Size and Decline): Does not meet criterion - total population size > than 10,000.

Criterion D: (Very Small Population or Restricted Distribution): Does not meet criterion - population size > than 1,000 and Area of Occupancy > than 20 km².

Criterion E: (Quantitative Analysis): None

Page details

Date modified: