Ferruginous hawk (Buteo regalis) COSEWIC assessment and status report: chapter 11
Technical Summary
Buteo regalis
Ferruginous Hawk – Buse rouilleuse
Range of Occurrence in Canada:
Alberta, Saskatchewan, Manitoba
Extent and Area Information
Extent of occurrence (EO) (km²)
(NatureServe digital range map data) : 206,000 km²
Specify trend in EO :
Decline, at least historically
Are there extreme fluctuations in EO?
No
Area of occupancy (AO) (km²)
assuming pairs use territories of 10 km² each : Ca. 9600-12,000 km²
Specify trend in AO :
Decline, at least in Alberta
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 :
Declining, at least historically
Population Information
Generation time (average age of parents in the population)
(adult annual mortality 30%, first breed at 2 years of age): Ca. 5 years
Number of mature individuals
- Alberta: 618 pairs;
- Saskatchewan: 300-500 pairs;
- Manitoba: 44 pairs.
- Total: Ca. 1200 pairs
Total population trend:
Declining in AB and MB, trend in SK unknown but likely declining
% decline over the last/next 10 years or 3 generations.
64% over last 13 years in AB (less than 3 generations); similar trend in Manitoba; no suitable data available from SK
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):
- Native grassland loss, degradation and fragmentation
- Declining prey populations
- Disturbance from oil and gas exploration
Rescue Effect (immigration from an outside source)
Status of outside population(s)?
USA: Occurs in 17 states apparently declining in 13 of them
Is immigration known or possible?
Possible
Would immigrants be adapted to survive in Canada?
Yes
Is there sufficient habitat for immigrants in Canada?
No
Is rescue from outside populations likely?
Unlikely
Quantitative Analysis
Not done
Current Status
COSEWIC: Special Concern (1995), Threatened (2008)
Status and Reasons for Designation
Status: Threatened
Alpha-numeric code: A2b
Reasons for Designation: This large hawk is found primarily on natural grasslands in southern Alberta, Saskatchewan and Manitoba and is a specialist predator on Richardson’s ground squirrels. It suffered a 64% decline in population from 1992 to 2005; since Alberta comprises the majority of the Canadian range, this implies a decline of at least 30% across the Prairies over that time period. The loss, degradation and fragmentation of its native grassland habitat are the most serious threats to the population.
Applicability of Criteria
- Criterion A (Declining Total Population): Meets Threatened A2b because of a known 64% decline over 3 generations in Alberta can be inferred to translate into at least a 30% decline throughout the Canadian range in the absence of trend data from Saskatchewan.
- Criterion B (Small Distribution, and Decline or Fluctuation): Not applicable. Distribution too large.
- Criterion C (Small Total Population Size and Decline): Not applicable. Population seems stable overall.
- Criterion D (Very Small Population or Restricted Distribution): Not applicable. Population and distribution too large.
- Criterion E (Quantitative Analysis): Not done.
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