Two subspecies of Burrowing Owl occur in North America: the Florida Burrowing Owl
(Speotyto cunicularia floridans), which is found primarily in Florida and on the Bahama Islands, and the western Burrowing Owl
(Speotyto cunicularia hyppgaea), which is found throughout Mexico, the western United States, and southwestern Canada. Although populations of the Florida Burrowing Owl are stable and at no risk of extinction, there has been widespread national and international concern in recent years about declines in populations of the western Burrowing Owl.
In Alberta, the Burrowing Owl is classified as endangered under the Wildlife Act, and, in 1996, was included on the
Red List of species that are at risk in the province.
Specific habitat characteristics of sites occupied by Burrowing Owls vary with geographic location. The three basic attributes of nesting habitat for the western Burrowing Owl are available nest burrows, short or sparse vegetation, and open terrain. On the Canadian prairies, nests are found on flat to gently undulating, treeless plains. Ground squirrel and Black-tailed Prairie Dog burrows, Badger excavations, and occasionally fox dens are used for nesting, roosting, and
Burrowing Owls are most abundant in the
Mixedgrass and Dry
mixedgrass ecoregions of Alberta, and are seldom found in the aspen
parkland and fescue grass ecoregions of the province. Vegetation type does not appear to be important as long as it is kept short or sparse by soil or climatic conditions, grazing, haying, mowing, or burning. With present land-use practices, areas grazed by livestock provide the vast majority of nesting habitat for Burrowing Owls in Canada.
What is known, is that in addition to requiring an open area with an adequate nest burrow immediately surrounded by short vegetation, Burrowing Owls need enough permanent cover and tall vegetation within their foraging home range to supply a sufficient amount of small mammals and other prey.
Little is known about the habitat requirements of Burrowing Owls on their wintering grounds. However, the availability of burrows is assumed to be one important component of habitat use, as Burrowing Owls in Mexico and Texas have been observed only in association with burrows.
The Burrowing Owl is a predator of small
vertebrates and invertebrates. Early in the breeding season, many dung and carrion beetles are eaten, and deer mice and voles constitute upwards of 90% of the diet. Later in the season, in some years, grasshoppers become more important in the diet, and are particularly important prey for fledglings learning to hunt on their own.
The Burrowing Owl is a small owl, that typically arrives in Alberta between early April and early May, depending on the harshness of spring weather.
Because these owls are small and do not nest in trees like most other raptors, they have many potential predators. Their predators are of two general types: predators that enter or dig up burrows (eating eggs, and nestlings) as well as predators that prey on older nestlings and adults when they are above ground. In Alberta, animals that can potentially access nest chambers are Badgers, foxes, Striped Skunks, Least and Long-tailed Weasels, Raccoons, Prairie Rattlesnakes and Bull Snakes. Animals that mainly catch owls above ground are Coyotes, Domestic Dogs and Cats, Great Homed Owls, Northern Harriers, Shorteared Owls, Prairie Falcons, and many types of Hawk. Badgers, Striped Skunks and Long-tailed Weasels seem to present the most serious threats to female Burrowing Owls and their eggs/nestlings, whereas avian predators cause the majority of mortalities in adult males and fledglings.
Burrowing Owls migrate from Alberta between early September and mid-October. Migration routes and the location of wintering grounds are unknown, but the owls probably spend the non-breeding season at least as far south as northern Mexico. Nest sites in Alberta may be reoccupied from year to year, but often different individuals may inhabit these nest sites each year.
Reprinted from Alberta Wildlife Status Report No. 11 (1997), with permission
from Alberta Sustainable