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BC Conservation Data Centre: Conservation Status Report

Aegolius acadicus brooksi
Northern Saw-whet Owl, brooksi subspecies

 
Scientific Name: Aegolius acadicus brooksi
English Name: Northern Saw-whet Owl, brooksi subspecies
   
Provincial Status Summary
Status: S2S3
Date Status Assigned: November 29, 2005
Date Last Reviewed: February 07, 2017
Reasons: A regional endemic, widely but sparsely distributed on Haida Gwaii. Large-scale forest harvesting outside of protected areas is significantly reducing available habitat including nesting sites.
 
Range
Range Extent: E = 5,000-20,000 square km
Range Extent Comments: This subspecies is restricted to Haida Gwaii which is just under 10,000 km squared (Am. Ornithol. Union 1957).
Area of Occupancy (km2): FG = 126-2,500
Area of Occupancy Comments: Estimated approximately 7000 km squared. This includes fragmented regenerating habitat where the owls will be found at a lower density and the old forest, occupied at a higher density (Holschuh 2004). (200 km 2 using the grid method)
 
Occurrences & Population
Number of Occurrences: C = 21 - 80
Comments: Based on COSEWIC (2006), although overall this is difficult to estimate as this subspecies is widespread across the archipelago and there may be few gaps of greater than the separation distance of 5km.
Number of Occurrences with Good Viability / Ecological Integrity: Rank Factor not assessed
Number of Occurrences Appropriately Protected & Managed: BC = 1 - 12
Comments: Several breeding areas are protected, mostly within Gwaii Haanas National Park Reserve on south Moresby Island, but smaller areas may also protect one or two pairs (e.g. Drizzle Lake Ecological Reserve).
Population Size: D = 1,000 - 2,500 individuals
Comments: COSEWIC (2006) suggests 926 breeding pairs +/- 290 based on survey data applied to density estimates for variable habitat quality types. Status review in 2005: There have been 3 systematic surveys conducted; in 1996 there were 61 individual owl locations identified and five singing trees, but no nests were located (Gill and Cannings 1996), 2002 and 2003 the likely habitats in the southern half of Graham Island were surveyed and in 2004 Gwaii Haanas was surveyed with a goal to determine range and density (Holschuh 2004). Using these numbers and the amount of fragmented/altered landscape and relatively undisturbed forest a population estimate of 1900 owls + or - 600 was determined (Holschuh 2004).
 
Threats (to population, occurrences, or area affected)
Degree of Threat: C = Medium
Comments: This subspecies is moderately threatened by large-scale harvesting of old-growth forest habitats on Graham Island and northern Moresby Island. Young regenerating forests may be suitable for roosting, but lack the structural features found in breeding and foraging habitat. This is further compounded by the introduction of Sitka black-tailed deer which have drastically altered the forest understorey as well, likely affecting the availability of rodent prey items (Cannings 1993). Other introduced species such as racoons and red squirrels may be a threat as nest preditors (Holschuh 2004).

From Threats Calculator: The generation time for this species is taken as 5 years.
 
Trend (in population, range, area occupied, and/or condition of occurrences)
Short-Term Trend: F = Decline of 10-30%
Comments: A decline of 15% has been noted over the past decade. Status review comments from 2005 remain relevant regarding invasive species and historic forest practices are improtant to understand the scale of habitat recovery: There are not enough data to determine a trend based upon numbers of owls, however, based on the overall decline in available habitat, and the associated occupancy densities in the disturbed and undisturbed areas, an overall decline of 10% can be estimated over the past 10 years. If the decline is calculated for only the landbase available for harvest, a 25 % decline over the past 10 years can be estimated. The effects of other external factors including the introduction of exotic species, although likely negative, are not well understood and are not factored into these calculations (Holschuh 2004).
Long-Term Trend: AE = Decline of >30%
Comments: If the original population is estimated based on the original base of available habitat, it suggests there to have been approximately 1550 sites + 420, suggesting an approximately 40% decline in population since the start of large-scale harvest operations (Holschuh 2004).
 
Other Factors
Intrinsic Vulnerability: C=Not intrinsically vulnerable
Environmental Specificity: B=Narrow. Specialist or community with key requirements common.
Comments: Secondary cavity nester; old-growth dependent for foraging habitat/prey suitability.
Other Rank Considerations:
 
Information Gaps
Research Needs: Breeding and foraging habitat and requirements of the subspecies should be investigated for long-term sustainable management. Breeding territory size should be determined to facilitate delineating reserve areas.
The effects of invasive species and habitat fragmentation (timber harvesting) on reproductive success should also be investigated to help with species management, including determining size of researve areas.
Inventory Needs: Identification of breeding and foraging habitats using standards for terrestrial ecosystem mapping (Ecosystems Working Group 1995) using an appropriate species-habitat model (see Research below). Surveys for singing males in high suitability habitats should then be undertaken in areas identified by habitat mapping, to determine provincial distribution, centres of abundance, and relative densities.
 
Stewardship
Protection: The species should be included in the species list in the proposed Identified Wildlife Management Strategy under the Forest Practices Code of British Columbia Act. Procedures for the establishment of Wildlife Habitat Areas within critical habitats, and General Wildlife Measures to determine appropriate forest practices within established areas, should be made available to resource managers.
Management: Potential Saw-whet Owl habitat should be surveyed prior to timber harvest to confirm the presence of resident owls. Logging should be avoided in occupied habitats from late March to early April to prevent desertion of nests by female owls (Cannings 1993). A substantial component of mature and over-mature trees and snags should be retained to provide nesting habitat. Since Northern Saw-whet Owls generally accept nest boxes, these could be used to mitigate impacts associated with loss of nesting snags, providing sufficient foraging habitat is retained (Cannings 1993). Once populations have been sufficiently inventoried, a status report and management plan for the Queen Charlotte subspecies should be prepared. Little is known of the biology of this subspecies (Gill and Cannings 1997).
 
Version
Author: L. Ramsay and S.G. Cannings; A.M. van Woudenberg
Date: March 22, 2018
 
References
American Ornithologists' Union. 1957. The American Ornithologists' Union check list of North American Birds, 5th ed., Baltimore, MD. 691pp.
B.C. Ministry of Water, Land and Air Protection. 2004. ?Queen Charlotte? Northern Saw-Whet Owl (Aegolius acadicus brooksi) in Accounts and Measures for Managing Identified Wildlife ? Accounts V. 2004. B.C. Ministry of Water, Land and Air Protection, Victoria, B.C.
Campbell, R.W., N.K. Dawe, I. McTaggart-Cowan, et al. 1990b. The Birds of British Columbia Vol. 2: Nonpasserines: Diurnal Birds of Prey through Woodpeckers. Royal British Columbia Museum, Victoria, BC.
Cannings, R.A., R.J. Cannings, and S.G. Cannings. 1987. Birds of the Okanagan Valley, B.C. Royal B.C. Mus., Victoria, BC. 420pp.
Cannings, R.J. 1993. Northern Saw-whet Owl (Aegolius acadicus) in A. Poole and F. Gill, eds. The Birds of North America, No. 42. Acad. Nat. Sci., Philadelphia, PA, and Am. Ornithol. Union, Washington, DC. 20pp.
Cannings, R.J. 1998. The Birds of British Columbia - a taxonomic catalogue. B.C. Minist. Environ., Lands and Parks, Wildl. Branch, Victoria, Wildl. Bull. B-86. 266pp.
COSEWIC. 2006w. COSEWIC assessment and status report on the Northern Saw-whet Owl brooksi subspecies Aegolius acadicus brooksi in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 23pp.
Gaston, A.J. 1994. Ancient Murrelet (Synthliboramphus antiquus). No. 132 in A. Poole, and F. Gill, eds., The Birds of North America. Acad. Nat. Sci., Philadelphia and Am. Ornithol. Union, Washington. 20pp.
Gill, M., and R.J. Cannings. 1997. Habitat selection of Northern Saw-whet Owls (Aegolius acadicus brooksi) on the Queen Charlotte Islands. North. For. Owl Symp., Winnipeg, MB, Feb. 1997, and Unpubl. rep. for B.C. Minist. Environ., Lands and Parks, Smithers, BC.
Godfrey, W.E. 1986. The Birds of Canada, rev. ed. Natl. Mus. Can., Ottawa, ON. 595pp.
Hobson, K.A., and S.G. Sealey. 1991. Marine protein contributions to the diet of northern saw-whet owls on the Queen Charlotte Islands: a stable isotope approach. Auk 108:437-440.
Holschuh, C.I. 2004. COSEWIC status report on Northern Saw-whet Owl, brooksi subspecies (Aegolius acadicus brooksi). Report prepared for the Committee on the Status of Endangered Wildlife in Canada. 25 pp.
Parks Canada Agency. 2014. Recovery Strategy for Northern Saw-whet Owl brooksi subspecies (Aegolius acadicus brooksi) in Canada [Final]. Species at Risk Act Recovery Strategy Series. Parks Canada Agency. Ottawa. vii + 34 pp.
Resource Inventory Committee. 1995. Standards for terrestrial ecosystem mapping in British Columbia: review draft. Ecosystems Working Group, B.C. Minist. Environ., Lands and Parks, Victoria, BC. 222pp.
Tamashiro, D. 1996. Genetic and morphological variation in Northern Saw-whet Owl populations in eastern North America. M.Sc. Thesis. Appalachian State Univ., Boone, NC.
 

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Suggested Citation:

B.C. Conservation Data Centre. 2018. Conservation Status Report: Aegolius acadicus brooksi. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Mar 30, 2026).