Short-eared owl (Asio flammeus) COSEWIC assessment and status report: chapter 5
Habitat
Habitat requirements
Short-eared Owls breed in a large number of open habitats including grasslands, arctic tundra, taiga, bogs, marshes, old pastures, and sand-sage. They also occasionally breed in agricultural fields (Herkert et al. 1999), although their breeding success in such habitats is apparently low (Campbell et al. 1990, Cadman and Page 1994). In arctic regions, breeding habitat is primarily arctic tundra and estuaries (Sinclair et al. 2003). In the Canadian Maritime provinces, Short-eared Owls breed primarily in well-drained grasslands near coastal wetlands (Erskine 1992, Schmelzer 2005). In areas with extensive coastlines, some caution is warranted in summarizing breeding habitat as inland marshes and bogs are less frequently monitored and thus may be under-represented in assessments of breeding habitat (e.g., Gauthier and Aubry 1996).
Preferred nesting sites are areas of dense grassland, as well as tundra with areas of small willows (e.g., at Churchill, Manitoba; Jehl 2004). However, as with habitat selection in general, the primary factor determining Short-eared Owl nest site choice is likely proximity to a reliable source of small mammal prey.
There is some evidence of annual and geographic variation in the degree to which Short-eared Owls defend territories during the breeding season, probably largely dependent on local prey abundance. Pitelka et al. (1955) stated that Short-eared Owls in northern Alaska showed little territorial behaviour, and only during the beginning of the nesting cycle. Clark (1975) also found a peak in territorial behaviour during the pre-nesting and early portions of the nesting cycle. In Manitoba, Clark (1975) found that mean territory size was 74 and 121 ha in successive years, with smaller territories during a year of high food abundance.
Trends
The distribution and abundance of Short-eared Owls prior to European settlement is unknown. Based on their current distribution, the main breeding areas were probably the Prairie Provinces, arctic and subarctic tundra/wetlands, and coastal wetlands.
Many regional ornithological studies have concluded that suitable breeding, migration, and wintering habitat has declined significantly in the past century, with consequent reductions in the number of owls (see Holt 1986, Campbell et al. 1990, Telfer 1992, Cadman and Page 1994, Smith 1996, Clayton 2000). The primary form of habitat loss occurs when grasslands are converted to agricultural crops (e.g., Smith 1991), but also includes losses due to recreational activities, resort development, and urban expansion (Holt 1986, Campbell et al. 1990). These latter three factors are an acute problem at coastal breeding and wintering sites. Grassland habitats also become unsuitable when heavily grazed by livestock (e.g., Fondell and Ball 2004). Telfer (1992) estimated a loss of 39% of the native grasslands throughout the range of the Short-eared Owl in Canadian Prairie Provinces between 1949 and 1986.
Protection/ownership
Outside the arctic coastal regions, the majority of suitable (e.g., grassland, old pastures, coastal wetlands) Short-eared Owl habitat in Canada is under private or Crown/Provincial ownership. Most habitat protection programs are being carried out through voluntary land stewardship programs. Efforts underway in Alberta (Operation Grassland Community) and Saskatchewan (Operation Burrowing Owl) to preserve and enhance grassland habitats are likely having significant positive effects on Short-eared Owls (T. Wellicome, pers. comm.).
Federal land-use incentive programs in Canada (the now defunct Permanent Cover Programs I & II) and the United States (e.g., Conservation Reserve Program, Wetland Reserve Program) have provided greatly increased grassland and wetland habitat coverage, with likely benefits for Short-eared Owls. In the United States, current enrollment in Grassland and Wetland Reserve Programs exceeds 30 million acres of former agricultural land (U.S. Dept. of Agriculture). The Alternate Land Use Services (ALUS) program has recently been implemented in Manitoba and is under consideration in other provinces. ALUS provides incentives for landowners to set aside marginal agricultural land and would therefore be of great benefit to Short-eared Owls. The recently proposed Conservation Cover Incentive Program (CCIP), which would mimic the CRP program in the United States, would also be highly beneficial to Short-eared Owls by providing breeding and foraging habitat. Finally, programs (e.g., Ducks Unlimited, Prairie Habitat Joint Venture) primarily administered to help breeding and migratory populations of waterfowl are highly beneficial given that wetland sites within grassland areas are also a primary breeding habitat for Short-eared Owls.
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