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Boreal Owl - Aegolius funereus
Potential Species of Concern Native Species Global Rank :
G5
State Rank :
S3S4
(see State Rank Reason below)
Agency Status USFWS :
MBTA
USFS :
BLM :
FWP SWAP :
SGIN
PIF :
3
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Copyright by Borror Laboratory of Bioacoustics, Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, OH, all rights reserved.
State Rank Reason (see State Rank above)
Very little is known about population size or population trends and there is concern over the impacts of forest disease, fire, and timber harvest because the species is dependent on mature spruce/fir forests.
Details on Status Ranking and Review
Boreal Owl (Aegolius funereus ) Conservation Status Review
Population Size
Score U - Unknown
Comment Unknown.
Range Extent
Score F - 20,000-200,000 km squared (about 8,000-80,000 square miles)
Comment 144,902 square kilometers based on Natural Heritage Program range maps that appear on the Montana Field Guide.
Area of Occupancy
Score U - Unknown
Comment Unknown.
Long-term Trend
Score U/E - Unknown, but believed to be relatively stable (±25% change)
Comment BNA account reports long-term trends as unavailable.
Short-term Trend
Score U/E - Unknown, but believed to be stable with population, range, area occupied, and/or number or condition of occurrences unchanged or remaining within ±10% fluctuation
Comment No trend data available.
Threats
Score B - Moderate and imminent threat. Threat is moderate to severe and imminent for a significant proportion (20-60%) of the population or area.
Comment Fire, disease, and timber harvest probably represent the greatest threats to the species since it is dependent on mature spruce/fir forests.
Severity Moderate - Major reduction of species population or long-term degradation or reduction of habitat in Montana, requiring 50-100 years for recovery.
Comment Mature forests require more than 50 years to regenerate after fire, disease, or timber harvest.
Scope Moderate - 20-60% of total population or area affected
Comment >20% of mature sprucke/fir forests in western Montana are being impacted or threatened by disease, fire, or timber harvest.
Immediacy Moderate - Threat is likely to be operational within 2-5 years.
Comment Ongoing
Intrinsic Vulnerability
Score C - Not Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance; or species has high dispersal capability such that extirpated populations soon become reestablished through natural recolonization (unaided by humans).
Comment Not Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has a high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance. Species has good dispersal capabilities such that extirpated populations generally become reestablished through natural recolonization.
Environmental Specificity
Score B - Narrow. Specialist. Specific habitat(s) or other abiotic and/or biotic factors (see above) are used or required by the Element, but these key requirements are common and within the generalized range of the species within the area of interest.
Comment Narrow Specialist. Associated with boreal spruce/fir forest.
General Description
Round-headed, although head appears rectangular. Eyes yellow, bill yellow/white. Facial disk white, surrounded by distinct black trim. Forehead spotted. Ventrally, white with brown vertical streaks along chest, sides, and flanks. Dorsally, brown with large conspicuous white spots. Juveniles have a dark brown/black facial disk, white forehead, and are light chocolate brown throughout the upper chest, grading into light brown on the belly. By early winter, juveniles resemble adults in plumage. SIZE: nine to 11 inches. WEIGHT: four to six ounces. VOICE: "To, to, to, to" given rapidly and varying in number. Voice is similar to Common Snipe.
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see
Marks et al. 2016, Birds of Montana. Diagnostic Characteristics
Saw-whet Owl is smaller, bill is black, has reddish/brown on the facial disk, and ventral streaking.
Species Range
Montana Range
Range Descriptions
Year-round
Western Hemisphere Range
Observations in Montana Natural Heritage Program Database
Number of Observations: 527
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
SUMMER (Feb 16 - Dec 14)
Direct Evidence of Breeding
Indirect Evidence of Breeding
No Evidence of Breeding
WINTER (Dec 15 - Feb 15)
Regularly Observed
Not Regularly Observed
(Observations spanning multiple months or years are excluded from time charts)
Migration
Resident and migratory, with some elevational migration. In Idaho, owls tended to use higher elevations during summer, but overlap between seasons was complete (Hayward 1989). Owls dispersed in years of poor prey concentration in Idaho, and the more northerly populations were more nomadic (Hayward and Verner 1994).
Habitat
High elevation spruce/fir forest, with lodgepole pine sometimes present. Mature spruce/fir forests with multilayered canopies and a highly complex structure, at elevations greater than 1500m with a mosaic of openings or meadows (Hayward 1989). In central Idaho, owls nested in mixed conifer (40%), spruce-fir (18%) Douglas-fir (21%) and aspen stands (21%) (Hayward 1989). One nest in MT was found in a dead broken-topped subalpine fir; nest opening measured 73X64 mm (Holt and Ermatinger 1989). Nests in MT have been exclusively lodgepole pine and spruce fir; no owls were found below 1292m in MT or ID (75% occurred above 1584m) (Hayward and Verner 1994).
Ecological Systems Associated with this Species
Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system,
even if point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at:
mtnhp.org/requests ) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
Literature Cited
Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
Commonly Associated with these Ecological SystemsForest and Woodland Systems
Grassland Systems
Recently Disturbed or Modified
Wetland and Riparian Systems
Occasionally Associated with these Ecological SystemsForest and Woodland Systems
Wetland and Riparian Systems
Food Habits
Predominately small mammals, with a few birds and insects. The Red-backed Vole is the main prey species in ID and CO. Other vole species taken when available along with other small rodents, birds, and insects (Palmer and Ryder 1984, Hayward 1989). Small mammals constitute 79% of their prey (Hayward and Verner 1994).
Ecology
Boreal Owls roost at sites scattered throughout their home range, rarely in the same stand on consecutive nights or the same tree more than 2X per year; they selected cool micro-sites in summer (Hayward 1989). They roost alone, usually far from their nest and mate. Owls use a sit-and-wait hunting method (Hayward 1989). Marten are the most important predator of owlets and adult females at the nest site; Red Squirrel predation upon eggs is also suspected in Idaho; large range: both winter and summer average over 1000 ha (Hayward and Verner 1994). Young Boreal Owls frequently disperse long distances from natal sites; in Finland, median distances of 88 and 21 km between juvenile male and juvenile female banding sites were reported; 20% of recoveries for owls marked as nestlings exceed 100 km in West Germany and 51% in Finland (Hayward and Verner 1994). This system of long distance dispersal results in high genetic connectivity and minimal genetic structuring of North American Boreal Owl populations, regardless of the habitat matrix they are associated with (Koopman et al. 2007).
Reproductive Characteristics
Begins nesting in late March or April. Nests in woodpecker holes or possibly natural cavities. Clutch size two to six. Incubation approximately 28 days. Young fledge at approximately 30 days. Probably breeds throughout its range in Montana. One nest in MT fledged young June 20 to 24 (Holt and Ermatinger 1989). In Idaho, males start singing in late January, females in early February; call rates increase through March. Egg laying takes place April 12 to May 24. Fledging takes 27 to 32 days (Hayward 1989). Monogamous for 1 breeding season; pair bond lasts for single season and most individuals nest with new mate each year (Hayward and Verner 1994).
Management
Management practices include retaining large-diameter snags in clearcuts, placing systems of nest boxes for population monitoring, and retaining large-diameter aspen for nesting where it is a component of coniferous forests. Spruce-fir succession is slow; as a result, clearcut sites may require 100 years to regain suitability for roosting and foraging, and 200 years to provide new nest trees. (Hayward and Hayward 1993)
References
Literature Cited AboveLegend: Aegolius funereus ). Species Account Number 063. The Birds of North America Online (A. Poole, Ed.). Ithaca, NY: Cornell Laboratory of Ornithology; Retrieved 3/25/2008 from The Birds of North America Online database
Additional ReferencesLegend: Do you know of a citation we're missing? Effects of recreation on Rocky Mountain wildlife: a review for Montana . [Montana]: Montana Chapter of the Wildlife Society.
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