COSEWIC Assessment and Status Report on the Chimney Swift in Canada
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures and Tables
- Species Information
- Population Size and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Technical Summary
- Acknowledgements and Information Sources
- Biographical Summaries of Report Writers
Extent and Area Information
Specify trend in EO
Are there extreme fluctuations in EO?
Area of occupancy (AO) (km2)
165 000 km2 from Ontario and Quebec breeding bird atlases (100 km2 per occupied atlas square) plus an estimated 35 000 km2 in prairies and Atlantic Canada.
ca. 200 000 km2
Specify trend in AO (Breeding Bird Atlases)
-46% over 20 years (1985-2004) Ontario
-35% over 15 years (1989-2004) in Quebec
ca. 33% decline over 13.5 years (3 generations; average of ON and QC data)
Are there extreme fluctuations in AO?
Number of known or inferred current locations
Specify trend in #
Are there extreme fluctuations in number of locations?
Specify trend in area, extent or quality of habitat
Number of mature individuals
Ca. 11 820
Total population trend:
% decline over the last/next 10 years or 3 generations.
Data from Breeding Bird Survey, annual decline of 2.4% over last 15 years
ca. 28% decline over last 3 generations (13.5 years);
>95% decline since 1968
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: Not applicable
Threats (actual or imminent threats to populations or habitats)
- Loss of nest and roost sites--initially through logging of old-growth forests, more recently through loss of chimneys suitable for nests and roosts.
- Part of an aerial insectivore guild, including swallows and nighthawks, that is showing significant declines throughout the Americas; the reasons for this widespread decline are unknown.
Rescue Effect (immigration from an outside source)
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?
Analysis suggests a 10% chance of extinction within 100 years if only 30% of birds 2 years of age and older breed.
COSEWIC: Threatened (2007)
Status and Reasons for Designation
Reasons for Designation: The Canadian population of Chimney Swift has declined by almost 30% over the last three generations (13.5 years) and the area it occupies has declined by a third over the same time period. The estimated Canadian population is about 12 000 individuals. Many aerial insectivores, including the Chimney Swift, swallows and nighthawks, have suffered population declines throughout the Americas over the past 30 years. The causes for these widespread declines are unknown but likely involve impacts to insect populations through pesticide use and habitat loss. Of this species group, the Chimney Swift has had the most serious known decline, probably because of the steadily decreasing number of suitable chimneys that the swifts use for nesting and roosting. Very few natural sites (large hollow trees) exist and current forest management regimes make it unlikely that many more will be available in the future. Chimney Swifts may experience significant mortality if hurricanes cross migratory paths; this could become a more important source of population loss if the frequency of these storms increase in the future as some climate models suggest.
Applicability of Criteria
Criterion A (Declining Total Population):
Meets Threatened A2c because of decline in Area of Occupancy (33% over 3 generations). Actual population decline estimates over 3 generations (28%) do not meet the A2b criterion, though declines were much steeper just prior to the 3-generation time period (95% population decline over 34 years).
Criterion B (Small Distribution, and Decline or Fluctuation):
Not applicable; range too large
Criterion C (Small Total Population Size and Decline):
Estimated population (11 820) slightly too large, although decline criterion is met for Threatened (28%).
Criterion D (Very Small Population or Restricted Distribution):
Criterion E (Quantitative Analysis):
a 10% chance of extinction over 100 years is predicted if all one-year-old birds are prevented from breeding because of lack of nest sites, but the data underlying this analysis were considered too unreliable to use this as an assessment criterion.
- Date Modified: