Conservation and Management

Sensitivity And Disturbance At Nest

Generally not sensitive to human activity as nests are difficult to locate (Leasure and Holt 1991). Human disturbance at nest site during pre-laying resulted in 3 of 4 females moving a short distance and re-nesting (Holt 1992). For research activities, trapping most effective with noose carpet (Bloom 1987) and mist-net for females (Leasure and Holt 1991). Artificial perch structures also provide successful substrates for trapping (Hall et al. 1981). Leasure and Holt (1991) observed no nest abandonment when females were trapped 10 d after the first young hatched.

Shooting And Trapping

Historically this species was shot (e.g., Bent 1938, Clark 1975); current impact of shooting on populations unknown but probably much lower than during historical times.  Rarely, vulnerable to collisions with barbed wire fences (Fig. 8).

Pesticides And Contaminants

Generally low concentrations with little effect on egg viability or health of adults. Mean levels of DDE in 5 Short-eared Owl eggs from the Canadian prairies 1960s: 0.5 ppm (Keith and Gruchy 1972). Wet weight organochlorine levels in tissue samples collected in 1968 include: muscle (DDE = 0.04, 0.10, 2.69 ppm, n = 3); brain (DDE = 0.01, 0.43, 0.05 ppm, n = 3); muscle (DDD = trace, 0.03, 0.10 ppm, n = 3); brain (DDD = 0 .01, 0.03 ppm, n = 3); muscle (DDT = trace, 0.02, 0.05, 0.22 ppm, n = 3); brain (DDT = 0.02, 0.08, n = 3); muscle (Dieldrin = trace, 0.01, 0.03 ppm, n = 3); brain (Dieldrin = trace, 0.02 ppm, n = 3; Peakall and Kemp 1980). In Israel, 5 Short-eared Owls were found dead, 4 paralyzed, in a field sprayed with Azodrin (an organophosphate) to control a vole outbreak; paralyzed birds later treated and released (Mendelssohn and Paz 1977).

Although organochlorine residues magnify with successive trophic levels in the food chain, birds of prey (such as Short-eared Owls) that eat mostly herbiverous mammals usually accumulate low levels. The low values reported above generally have little effect on eggshell thickness and breakage, tissue damage, or embryo mortality.

Degradation Of Habitat

Nesting habits and nomadism make this species particularly vulnerable to habitat loss at any season; such loss—conversion of open habitats to agriculture, grazing, recreation, housing, and resort development—a key factor in declines (Holt 1986b, Melvin et al. 1989, Campbell et al. 1990, Tate 1992). Reforestation in some areas may also contribute to habitat loss. Predation by striped skunks (Mephitis mephitis) on eggs and nestlings suspected in decline on Martha’s Vinyard Is., MA (Melvin et al. 1989) and disturbance at nests by domestic and feral cats and dogs is known (Tate 1992). Interspecific competition with Barn Owls (Tyto alba) may also occur; successful nest box programs to attract Barn Owls have coincided with the decline of the Short-eared Owl on Martha’s Vineyard and Nantucket Is., Massachusetts.

Short-eared Owls appear particularly sensitive to habitat loss and fragmentation, as they require relatively large tracts of grassland and are ground nesters, making them susceptible to the increased predation pressure that is typical within fragmented habitats and near rural developments. The development of conservation/management plans for this owl has been hampered by difficulty in accurately assessing their local and regional status, and by a lack of information on reproductive success. Although they are listed as a Bird of Conservation Concern by the U.S. Fish and Wildlife Service, as well as a Priority species within many state and regional Partners in Flight bird conservation plans, no research programs on the conservation status of short-eared owls are currently underway. The loss of open grassland habitats on the Great Plains and along the Pacific and northern Atlantic coasts has been cited in a number of studies as the primary causative factor behind recent declines in Short-eared Owls in those areas. On the Great Plains, the primary sources of habitat loss have been the conversion of native prairie to agricultural use and overgrazing of existing grasslands. Along coastal areas, which include many wintering sites, recreational use and land development have caused losses of nearshore marsh and oldfield habitats. Habitat restoration programs, such as the Conservation and Wetland Reserve Programs, have shown some success in restoring suitable habitat for short-eared owls on private land. Such programs not only provide suitable nesting and wintering habitat, but they may also help to restore small mammal populations, which are the key resource responsible for population fluctuations of owls. However, it is important to note that large blocks of habitat are essential for short-eared owls, and habitat preservation/restoration programs should aim to conserve large blocks of habitat (>100 ha).

Measures Proposed And Taken

In Massachusetts (Massachusetts Natural Heritage Program), management suggestions have included: standardized survey protocol, maintaining large continuous tracts of habitat for the owls and their prey, monitoring predation and human disturbance, public education, and research. Species has benefited indirectly from protection of nesting cover for waterfowl (Larsen 1987, DWH); also from reclaimed and replanted strip-mines and dikeland (Tate 1992). Burning and maintenance of grasslands for gallinaceous birds and waterfowl provides nesting and foraging cover for this owl (Millsap et al. 1987).

In Illinois, Herkert et al. 1999 showed that the species requires shorter grass than is provided by most idle grasslands in the Midwest, so burning and/or mowing are needed to reduce overall grass height and provide suitable habitat. 

See also http://www.npwrc.usgs.gov/resource/literatr/grasbird/seow/seow.htm, which focuses on western portions of the range and the need to keep cover short by burning, mowing, etc.