Asio flammeus (Pontoppidan, 1763)
Basis for Listing
The Short-eared Owl (Asio flammeus) is distributed throughout much of the world, occurring on every continent except Australia and Antarctica. In North America, this species ranges from the Arctic tundra south to Mexico and the Caribbean. Concern regarding its status in the United States has been raised in several parts of its range, particularly in the northern and eastern regions. It has been on the National Audubon Society's Blue List since 1976. The Short-eared Owl was once a common and widespread summer resident in Minnesota. Although little is known of its exact breeding range, the species occurred widely during the first half of the twentieth century and was frequently observed throughout the state, except in the northeastern and southeastern regions.
The Short-eared Owl is a medium-sized buffy-brown owl with long wings. Unlike most other owls, this species is most often seen flying low over open grasslands during the day, especially at dawn and dusk. In flight, Short-eared Owls are best identified by the dark wrist marks and black wing tips on the underside of the wings and the buff-colored patch near the base of the primaries on the upperside. The species' distinctive flight pattern is bouncy, agile, and rather moth-like. Diurnal activity and lighter plumage, with more prominent wing markings, distinguish this species from the Long-eared Owl (Asio otus) (Wiggins et al. 2020).
Short-eared Owls are found in open habitats such as native prairie (upland and lowland prairie), pasture, Conservation Reserve Program grasslands, sedge wetlands (wet meadow/carr), shrub swamps, and open peatlands (non-forested acid peatland and non-forested rich peatland). They are most often found in extensive tracts of habitat, rather than small, isolated patches, particularly during the breeding season. In the winter and during migration, Short-eared Owls will use a variety of open country habitats.
Biology / Life History
Banding data show seasonal migrations of the Short-eared Owl, especially in the northern part of its range. A nomadic species, the Short-eared Owl responds to fluctuating small mammal populations and is particularly responsive to vole and lemming populations. Because the Short-eared Owl moves in response to its food supply, it may remain to breed in atypical breeding habitat if small mammals are abundant (Clark 1975; Wiggins et al. 2020). The species feeds mainly on voles in North America. Other small mammals and some birds are also taken. The Short-eared Owl hunts both day and night, though winter hunting may occur primarily at dawn and dusk. It hunts while flying and uses both auditory and visual cues in detecting prey. When prey is located, the bird may hover before striking (Wiggins et al. 2020). Short-eared Owls are seasonally monogamous or polygamous. During the mating season, males vocalize at night with a "voo-hoo-hoo-hoo-hoo" song. Both adults typically defend the nest vigorously by barking, screaming, or enacting distraction displays. Short-eared Owls are ground nesters. The female chooses a dry site, scrapes out a bowl-like area, and lines it with grasses and feathers. Eggs are cream-colored and incubated only by the female. Upon hatching, young are semi-altricial and able to walk out of the nest after 12-18 days. They can fly after 24-35 days (Wiggins et al. 2020). Short-eared Owls roost and sleep mainly on the ground. During fall and winter, they may gather in communal tree roosts, frequently with long-eared owls (Wiggins et al. 2020).
Conservation / Management
Breeding bird surveys from 1966-2015 indicate a 1% annual decline throughout its North American range over this time period (Sauer et al. 2017). Habitat loss and degradation, including conversion of native open habitats to agriculture and reforestation of open lands, are the main factors affecting Short-eared Owl populations. Protection and management of peatlands and native grasslands for waterfowl can also benefit Short-eared Owl populations as well as populations of small mammals, their main prey (Wiggins et al. 2020). Because Short-eared Owls nest on the ground in open areas, their eggs are highly vulnerable to mammalian predators, such as fox (Vulpes spp.), Raccoon (Procyon lotor), weasels (Mustela spp.), skunk, cats, and dogs (NatureServe 2020). Predator control programs that are used to benefit other ground nesting birds will also benefit this species. Avian predators, such as Herring Gulls (Larus argentatus) and various raptors, also pose a threat to nestlings and adults (Wiggins et al. 2020). Additionally, illegal hunting by humans has played a role in the reduction of Short-eared Owl populations (NatureServe 2020). Public education programs that increase awareness of the value of this and all raptors in natural and agricultural environments would benefit this species.
Conservation Efforts in Minnesota
Few intensive Short-eared Owl surveys have been conducted in Minnesota. Although the species has been recorded during the breeding season in 21 counties since the 1970s, surveys conducted by the Minnesota Biological Survey (MBS) since 1987 have found Short-eared Owls at scattered locations in only six counties, primarily in the northwestern part of the state. Since 2010, public reports have continued in as many as 18 counties during the summer months, with the majority of observations also in the northwestern part of the state (Minnesota Ornithologists’ Union 2020). Continued breeding season inventories are needed to determine the Short-eared Owl's population status and to locate areas with current and potential nesting habitat. Expanded efforts to acquire, protect, and restore native grasslands are needed to preserve the disappearing habitats on which this species depends.
Bob Dunlap (MNDNR), 2022
(Note: all content ©MNDNR)
References and Additional Information
Clark, R. J. 1975. A field study of the Short-eared Owl, Asio flammeus (Pontoppidan), in North America. Wildlife Monographs 47:1-67.
Holt, D. W., and S. M. Leasure. 1993. Short-eared Owl (Asio flammeus). Number 61 in A. Poole and F. Gill, editors. The birds of North America. The Birds of North America, Inc., Philadelphia, Pennsylvania.
National Audubon Society [Audubon]. 2003. Audubon Watchlist: Short-eared Owl. Audubon home page.
NatureServe. 2008. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.0. NatureServe, Arlington, Virginia.