BC Conservation Data Centre: Conservation Status Report
Megascops kennicottii kennicottii
Western Screech-Owl, kennicottii subspecies
| Scientific Name: | Megascops kennicottii kennicottii |
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| Scientific Name Synonyms: |
Otus kennicottii kennicottii
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| English Name: | Western Screech-Owl, kennicottii subspecies |
| Provincial Status Summary | |
| Status: | S2S3 |
| Date Status Assigned: | May 16, 2017 |
| Date Last Reviewed: | March 15, 2017 |
| Reasons: | Apparent precipitous decline in numbers in core area of its range, i.e., lower mainland and southeast Vancouver Island, particularly since 2000, and earlier, in some areas. Preliminary analysis of Christmas Bird Count data from 1988 to 2004 indicated that on Vancouver Island numbers have declined 17% annually, while in the lower mainland numbers declined 32% annually (Elliot 2006). On the south coast of British Columbia, population decline is thought to be linked to the recent arrival of Barred Owls that are known to depredate and out-compete screech-owls. Barred Owls are expected to continue their range and density expansion northwards, potentially impacting screech-owl populations outside their core range. Urbanization and conversion of wooded areas to agricultural lands in the southern portion of the range reduces habitat. Populations are also impacted by forestry operations that reduce dead trees and snags that provide roosting and nesting cavities. |
| Range | |
| Range Extent: | F = 20,000-200,000 square km |
| Range Extent Estimate (km2): | 150,000 |
| Range Extent Comments: | Estimated extent of occurrence in British Columbia is 150,000 km2 (COSEWIC 2012). Breeds on Vancouver Island, the Gulf Islands, the mainland coast (Campbell et al. 1990). They probably breed west of the Coast Ranges along the length of the mainland coast to the Yukon border, although breeding has not been confirmed north of Kitimat (Campbell et al. 1990). Likely restricted to mature lowland coniferous and mixed forests below 600 m elevation (Campbell et al. 1990); however, regularly occurs to 900 m in suitable habitat on southern Vancouver Island (J. Hobbs unpubl. data). |
| Area of Occupancy (km2): | G = 501-2,500 |
| Area of Occupancy Comments: | In British Columbia, the estimated area of occupancy is 4000 km2. This based on an estimate of 1000 breeding pairs, each occupying a single 2 km X 2 km cell. The 1000 breeding pairs estimate is taken from the estimate of 2000 adults in the M. k. kennicottii population (COSEWIC 2012). |
| Occurrences & Population | |
| Number of Occurrences: | CD = 21 - 300 |
| Number of Occurrences with Good Viability / Ecological Integrity: | U = Unknown |
| Number of Occurrences Appropriately Protected & Managed: | U = Unknown |
| Comments: | Currently unknown, but probably at least 10 protected element occurrences. Previous to 2000, possibly >40 element occurrences were protected in British Columbia. Since 2000, or earlier, most previously known breeding sites have become abandoned in the lower mainland and southeast Vancouver Island (Elliot 2006; BSC 2008; D. Fraser pers. comm. Dec 2009; J. Hobbs pers. comm. Jan 2010). Protected occurrences in central and northern Vancouver Island may not have suffered such large declines as southern areas (COSEWIC 2002); but there is no data to confirm this. In the lower mainland, pre-2000 known protected breeding sites occurred in the following municipal and regional parks: Alaksen National Wildlife Area (Delta), Bear Creek Park (Surrey), Burnaby Lake Park (Burnaby), Burns Bog (Delta), Campbell Valley Park (Langley), Central Park (Burnaby), Crescent Park (Surrey), Deer Lake Park (Burnaby), Green Timbers Park (Surrey), Musqueam Park (Vancouver), Pacific Spirit Park (Vancouver), Redwood Park (Surrey), and Stanley Park (Vancouver) (Elliot 2006). On Vancouver Island and the Gulf Islands, previously known protected breeding sites occurred in many lower elevation protected areas, some of the larger protected areas being: Francis/King Regional Park (Victoria), Goldstream Provincial Park (Victoria), Helliwell Provincial Park (Hornby Island), and Pacific Rim National Park (Tofino), among others. |
| Population Size: | DE = 1,000 - 10,000 individuals |
| Comments: |
Based on surveys by Preston and Campbell (2001) density estimates were made for this subspecies, overlayed on suitable habitat and a total estimate of individuals determined (1940 individuals). This initial estimate was based on an even distribution of owls, which there is not. The densty declines further north and the population has declined greatly in the Victoria and Vancouver areas (Elliott 2006), therefore an overall population estimate of 1500-3000 is used (COSEWIC 2012). |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | AC = Very high - medium |
| Comments: | Although empirical data are lacking, it is widely believed that predation by Barred Owl is the main threat for Western Screech-Owls on south coastal British Columbia (COSEWIC 2002; Elliot 2006; D. Fraser pers. comm. Dec 2009; J. Hobbs pers. comm. Jan 2010). A growing amount of anecdotal evidence of Barred Owls preying upon (COSEWIC 2002; J. Hobbs pers. comm. Jan 2010) and aggressively responding (including striking surveyors) to Western Screech-Owl taped calls (Elliot 2006). On Vancouver Island and the lower mainland, Barred Owl numbers increased on Christmas Bird Counts over the same time period when Western Screech-Owls declined (Elliot 2006). Analysis of Christmas Bird Count data for Vancouver Island and the lower mainland between 1998 and 2002 found that Screech-owls declined first in Christmas Bird Count areas where Barred Owls numbers increased most rapidly and where Barred Owls numbers were the highest (Elliot 2006). Other threats for coastal Western Screech-Owl include habitat loss by forest harvesting, urbanization and conversion of wooded areas to agriculture. Forestry operations negatively affect screech-owl habitat both by the removal of habitat through timber harvesting and, for worker safety issues, the removal of dead trees and snags that provide potential nest cavities (COSEWIC 2002). However, the relationship between Western Screech-Owls and forestry has not been well studied. Urbanization and agricultural pressures typically occur at lower elevations, impacting preferred nesting habitat (Fraser et al. 1999; Robertson et al. 2000). Additionally, the expanded range of the introduced grey squirrel in urban and suburban areas of the lower mainland and southeast Vancouver Island likely has had a negative impact on Western Screech-Owls as they compete for cavities and depredate owlets (Elliot 2006). |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | E = Decline of 30-50% |
| Comments: |
There has been a greater than 90% loss in the metro Vancouver, Victoria and Gulf Islands areas, withan overall decrease estimated to be 20-30% between 1995 and 2010 (COSEWIC 2012). Christmas Bird Count data from the south coast of British Columbia provide evidence of a significant population decline of screech-owls in that area. Since CBCs began reporting owl survey effort data in 1983, the number of Western Screech-Owls on seven long-term counts (Duncan, Ladner, Nanaimo, Sunshine Coast, Vancouver, Victoria and White Rock) has dropped from a mean of one owl per hour to about one owl every 10 hours. Data from the British Columbia-Yukon Nocturnal Owl Survey shows a steep decline in Western Screech-Owl detections on the British Columbia coast between 2000 and 2004; there were no detections on that survey from 2005 to 2009 inclusive (COSEWIC 2012). Elliot (2006) suggested that by 2002, Western Screech-Owls had disappeared from 22 previously known breeding sites in the lower Fraser Valley monitored between 1998 and 2002. Nocturnal owl surveys using call playbacks conducted by volunteers on 18 coastal survey routes had zero screech-owl detections in both 2007 and 2008, compared to an average of approximately 0.3 detections per 10 survey stops between 2005 and 2006 (BSC 2008). ____________ ¿Recent surveys in the lower mainland (Elliot 2006) and coastal British Columbia (BSC 2008) have confirmed some of these declines. However, previous to 2000, Western Screech-Owls were typically one of the most common owl species detected in coastal British Columbia (COSEWIC 2002). For example, owl surveys in the Nimpkish Valley, north of Campbell River, detected between 61 and 102 individuals annually between 1995 and 1997, and were the most common owl of five owl species recorded (Setterington 1998). In Clayoquot Sound, on western Vancouver Island, Western Screech-Owls were also the most common of five owl species found during the breeding season (Holroyd et al. 2000). In a study in the Campbell River watershed, screech-owls were the second most common owl of four owl species detected (Mico and Van Enter 2000). __________________ Few data available, but likely significantly declining, particularly, in the core, or southern part, of its range along coastal British Columbia (COSEWIC 2002; Elliot 2006; BSC 2008; D. Fraser pers. comm. Dec 2009; J. Hobbs pers. comm. Jan 2010). Surveys conducted at 22 previously known breeding sites in the lower mainland between 1998 and 2002, had 14 screech-owl detections between 1998-2000 and no detections between 2001-2002 (Elliot 2006). By 2002, Elliot (2006) suggested that Western Screech-Owls had disappeared from most of Vancouver, Burnaby, Delta, Surrey and Langley. Many of these sites were previously surveyed between 1993 and 1998, when screech-owls were detected on 64% of 11 surveys (475 sampling points) in the lower Fraser Valley (Robertson et al. 2000). In both 2007 and 2008, nocturnal owl surveys using call playbacks had no Western Screech-Owl detections along 18 coastal survey routes (each consisting of at least 10 survey stops) in southern British Columbia (BSC 2008). In 2005 and 2006, the average detection rate was approximately 0.3 screech-owl detections per 10 survey stops for the same coastal survey routes (BSC 2008). |
| Long-Term Trend: | U = Unknown |
| Comments: | There aren't any long term data sets (COSEWIC 2012). Historic population numbers are unknown, but the current population is more than likely significantly lower than historic levels, considering recent declines. |
| Other Factors | |
| Intrinsic Vulnerability: | Rank Factor not assessed |
| Environmental Specificity: | B=Narrow. Specialist or community with key requirements common. |
| Comments: | Western Screech-Owls are non-migratory and depend year-round on older trees with cavities for roosting and during the breeding season for nesting. |
| Other Rank Considerations: | Up until 2002 there was a second subspecies of Otus kennicottii kennicottii was recognized and listed inthe southern portion of the range, Otus kennicottii saturatus. In 2002 it was dropped as a separate subspecies due to lack of evidence of separation. |
| Information Gaps | |
| Research Needs: | Research is required to determine the impact of predation and competition by Barred Owls. Forestry impacts are unclear and require study, particularly the impacts of habitat fragmentation on dispersal and immigration. Research is required on the impacts of dead tree and snag removal for forestry worker safety issues and firewood collection. Studies are required on optimum patch size for Western Screech-Owl and the apparent correlation between the species' recent persistence in smaller patch sizes (20 h +/- 8 ha) in the lower mainland as a possible response for avoiding Barred Owl predation, a species that tends to prefer larger forested patches (Robertson et al. 2000; Elliot 2006). |
| Inventory Needs: | Annual inventories of Western Screech-Owl and Barred Owls should be conducted in the core area of the screech-owl's range, i.e., lower mainland and southeast Vancouver Island, to document population trends and confirm predation impacts on screech-owls. |
| Stewardship | |
| Protection: | In local areas where habitat degradation has reduced the number of potential roosting and nesting cavities, effort should be made to erect artificial nest boxes. |
| Management: | |
| Version | |
| Author: | Ramsay, L. and Chytyk, P. |
| Date: | March 15, 2017 |
| References | |
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Campbell, R.W., N.K. Dawe, I. McTaggart-Cowan, J.M. Cooper, G.W. Kaiser, and M.C.E. McNall. 1990b. The Birds of British Columbia Vol. 2: Nonpasserines: Diurnal Birds of Prey through Woodpeckers. Royal British Columbia Museum, Victoria, BC.
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COSEWIC. 2012e. COSEWIC assessment and status report on the Western Screech-Owl kennicottii subspecies Megascops kennicottii kennicottii and the Western Screech-Owl macfarlanei subspecies Megascops kennicottii macfarlanei in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xii + 30 pp. (www.registrelep-sararegistry.gc.ca/default_e.cfm).
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Hekstra, G.P. 1982. Description of twenty-four new subspecies of American Otus. Bull. Zool. Mus. Univ. Van Amsterdam 9:49-63.
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Please visit the website Conservation Status Ranks for information on how the CDC determines conservation status ranks. For global conservation status reports and ranks, please visit the NatureServe website http://www.natureserve.org/.
Suggested Citation:
B.C. Conservation Data Centre. 2017. Conservation Status Report: Megascops kennicottii kennicottii. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Apr 24, 2024).