Short-eared owl (Asio flammeus) COSEWIC assessment and status report: chapter 11
Technical Summary
Asio flammeus
Short-eared Owl – Hibou des marais
Range of Occurrence in Canada:
All jurisdictions
Extent and Area information
extent of occurrence (EO) (km²) (from Partners in Flight Database) :
ca. 7,500,000 km²
specify trend (decline, stable, increasing, unknown) :
Stable
are there extreme fluctuations in EO (> 1 order of magnitude)?
No
area of occupancy (AO) (km²) guesstimate based on habitat availability :
ca. 1,500,000 km²
specify trend (decline, stable, increasing, unknown)--assumed based on population decline :
Decline
are there extreme fluctuations in AO (> 1 order magnitude)?
Probably not
number of extant locations :
Not applicable
specify trend in # locations (decline, stable, increasing, unknown) :
Not applicable
are there extreme fluctuations in # locations (>1 order of magnitude)?
Not applicable
habitat trend: specify declining, stable, increasing or unknown trend in area, extent or quality of habitat :
Habitat loss occurring in southern parts of Canadian range
Population information
generation time (average age of parents in the population) (indicate years, months, days, etc.) :
2 years
number of mature individuals (capable of reproduction) in the Canadian population (or, specify a range of plausible values)
from Partners in Flight estimates, based on Breeding Bird Survey and other data sources. Other estimates have been much lower (10,000-40,000). Ca. 350,000
total population trend: specify declining, stable, increasing or unknown trend in number of mature individuals
Declining
if decline, % decline over the last/next 10 years or 3 generations, whichever is greater (or specify if for shorter time period) :
27% over 10 years (Christmas Bird Count data)
are there extreme fluctuations in number of mature individuals (> 1 order of magnitude)?
Probably not
is the total population severely fragmented (most individuals found within small and relatively isolated (geographically or otherwise) populations between which there is little exchange, i.e., < 1 successful migrant / year)?
No
list each population and the number of mature individuals in each
specify trend in number of populations (decline, stable, increasing, unknown)
are there extreme fluctuations in number of populations (>1 order of magnitude)?
Threats (actual or imminent threats to populations or habitats)
- Loss and degradation of wintering habitat
- Loss and degradation of breeding habitat in southern Canada
- Pesticide use
Rescue Effect (immigration from an outside source) :
Moderate
does species exist elsewhere (in Canada or outside)?
Yes
status of the outside population(s)?
Declining
is immigration known or possible?
Yes
would immigrants be adapted to survive here?
Yes
is there sufficient habitat for immigrants here?
Unknown
Quantitative Analysis
Not done
Current Status
COSEWIC: Special Concern (April 1994 and April 2008)
Status and Reasons for Designation
Status: Special Concern
Alpha-numeric code: not applicable
Reasons for Designation: This owl has suffered a continuing population decline over the past 40 years, including a loss of 23% in the last decade alone. Habitat loss and degradation on its wintering grounds are most likely the major threat, while continuing habitat loss and degradation on its breeding grounds in southern Canada and pesticide use are secondary threats. This species nearly meets the criteria for Threatened status.
Applicability of Criteria
Criterion A: (Declining Total Population): Decline in last 10 years (23%) is too low to meet criterion for Threatened.
Criterion B: (Small Distribution, and Decline or Fluctuation): Distribution too large.
Criterion C: (Small Total Population Size and Decline): Population too large.
Criterion D: (Very Small Population or Restricted Distribution): Population and distribution too large.
Criterion E: (Quantitative Analysis): Not done.
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