Burrowing Owl (Athene cunicularia)
Associated Species: Other species that may use habitat in a similar way and/or respond similarly
to threats, management, and conservation activities include Ferruginous Hawk, Rough-legged
Hawk, Swainson's Hawk, Golden Eagle, Mountain Plover, and Horned Lark.
Distribution: Burrowing Owls nest from southern British Columbia east to southern Manitoba,
south to central Mexico, and west to Baja California; a disjunct population occurs in Florida. In
Colorado, Burrowing Owls breed throughout the eastern plains and in river valleys and mountain
Habitat Requirements: These owls reside in treeless areas with short vegetation (<10 cm; 4 in),
usually in association with prairie dog colonies. They nest in burrows dug by prairie dogs,
badgers, coyotes, or foxes. Some evidence suggests that they prefer larger prairie dog colonies,
perhaps because of decreased threat of predation.
Ecology: Some uncertainty surrounds the timing of specific breeding events by this species, due
to the relative difficulty of studying their underground nests. The owls arrive in Colorado at the
end of March and early April, and probably initiate nesting by early May. Fledged young appear
at the burrow opening from May through July. The birds leave for their wintering grounds in the
Southwest, Mexico, and Central America by mid October. The breeding season diet consists
primarily of insects, but small mammals are also taken.
Management Issues and Conservation Recommendations: Loss of native grassland by
conversion to agriculture results in loss of foraging and nesting habitat; urbanization also destroys
habitat and elevates levels of disturbance by humans (noise, harassment by pets, collisions with
vehicles). Maintain a 100 to 300 m (300-1,000 ft) buffer zone around Burrowing Owl nest
burrows and prohibit pesticide applications, rodent control, and other human disturbances
within this zone. Protect all colonies in Colorado's Front Range counties, where populations
have declined most precipitously.
Burrowing Owls in Physiographic Area 36 are heavily dependent on prairie dogs for burrows, for
burrow maintenance, and for the preferred low vegetation profile. Programs to control prairie
dogs are detrimental to owl populations because they lead to loss of breeding habitat, and because
some chemical controls are harmful to owls. Prairie dog management on private land should aim
to control rather than eradicate. Encourage private landowners to retain prairie dog populations
at the highest level compatible with economic activities on the land, to employ nonlethal means
of control (trapping and relocating, barrier fences), to treat only active prairie dog burrows, to
avoid burrows that show evidence of use by Burrowing Owls (presence of feathers or white
droppings, or entrances lined with livestock manure), and to fumigate burrows in the spring
before the owls arrive or bait in the fall after the owls have left.
Control of the principal prey species (grasshoppers, crickets, beetles) can also harm populations
because insecticides have direct (toxic) and indirect (loss of prey) effects on the birds. Postpone
the use of insecticides until after young owls have fledged (i.e., after the end of July).
Because these owls habitually perch on the ground outside of a burrow entrance, "varmint"
hunters occasionally mistake them for prairie dogs or ground squirrels and shoot them. Educate
hunters on the ecological importance of the owls and provide information on identification.
Status and Reasons for Concern: This species has a high conservation need locally and
throughout its range. A high proportion (estimated at 24.7%) of this species' total population
occurs within this physiographic area, indicating that this area has high responsibility for the
species' conservation. This is a USFS Sensitive Species in Region 2. Within Physiographic Area
36, BBS data do not show a statistically significant annual rate of change between 1966 and 1996
(P = 0.41; n = 45 routes). Burrowing Owls were present on an average of 54.02% (SE = 2.24) of
the BBS routes run in Physiographic Area 36 in Colorado during 1988-1997, at an average
abundance of 2.88 (SE = 0.30) individuals per route. The mean number of routes run each year
was 29.2 (SE = 2.28). This species is monitored by MCB with nocturnal surveys.
Biological Objective: Increase the species' distribution and abundance, based upon results from
the BBS and MCB monitoring programs.
Selected References: Andrews and Righter 1992, Haug et al. 1993, Kingery 1998, Pezzolesi