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COSEWIC Assessment and Update Status Report on the Ross’s Gull in Canada

Technical Summary

Rhodostethia rosea

Ross’s Gull

Mouette rosée

Range of Occurrence in Canada: Nunavut Territory and Manitoba

Extent and Area Information

Extent of occurrence (EO) (km2)
Calculated by including areas of all breeding locations, including historical ones (e.g. Cheyne Islands)
300 000 km2
Specify trend in EOUnknown
Are there extreme fluctuations in EO?No
Area of occupancy (AO) (km2)
Calculated by selecting the four known breeding locations and using a 50 km radius around each location
31 000 km2
Specify trend in AOUnknown
Are there extreme fluctuations in AO?No
Number of known or inferred current locations3 known in 2005/06: Churchill, Penny Strait, Cheyne Islands
Specify trend in #Unknown
Are there extreme fluctuations in number  of locations?No
Specify trend in area, extent or quality of habitatStable

Population Information

Generation time
(average age of parents in the population)
>10 years
Number of mature individualsUp to 20 observed, likely more
Total population trendUnknown, but likely stable
% decline over the last/next 10 years or 3 generationsUnknown
Are there extreme fluctuations in number of mature individuals?No
Is the total population severely fragmented?Based on known groups, yes
Specify trend in number of populationsStable
Are there extreme fluctuations in number  of populations?No
List populations with number of mature individuals in each: 1. Churchill – 4 (2005);  2: Penny Strait – 10 (2005); 3: Cheyne Islands – 6 (2006); 4: Prince Charles Island - ?

Threats (actual or imminent threats to populations or habitats)

Industrial development
Human disturbance
Climate change

Rescue Effect (immigration from an outside source)

Status of outside population(s)?
Major breeding population in Siberia; unknown trend, but possibly stable
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?Yes

Quantitative Analysis


Current Status

COSEWIC: Threatened (2001, 2007)

Status and Reason for Designation

Alpha-numeric code:
Met criterion for Endangered, D1, but designated Threatened, D1, because there is potential for rescue and because more birds likely occur in unsurveyed areas.
Reason for designation:
In Canada, this species is known to occur in small numbers in very few locations. Threats include disturbance in some breeding areas and changes in ice and snow patterns associated with climate change.

Applicability of Criteria

Criterion A (Declining Total Population):
Does not meet criterion.
Criterion B (Small Distribution, and Decline or Fluctuation):
Does not meet criterion.
Criterion C (Small Total Population Size and Decline):
Does not meet criterion.
Criterion D (Very Small Population or Restricted Distribution):
Meets D1 Endangered because known population < 250 mature individuals.
Criterion E (Quantitative Analysis):
No quantitative analyses.