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 parks elsewhere. Mesa County has the largest population in Physiographic Area 87 in Colorado.

Habitat Requirements: These owls inhabit treeless areas with short vegetation (<10 cm; 4 in), especially in association with colonies of prairie dogs or ground squirrels. The owls nest in burrows dug by the rodents, and prefer the extremely short vegetation found in the colonies. There is some evidence that they prefer larger prairie dog towns, 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: Programs to control the principal prey species (grasshoppers, crickets, beetles) are detrimental to Burrowing Owl populations, as the insecticides have direct and indirect effects on the birds. Postpone insecticide use until after young owls have fledged (i.e., after the end of July). To protect agricultural land, consider a grasshopper bait line only along the interface of agricultural and range land.

Control of prairie dogs and ground squirrels, upon which owls in the western U.S. are totally dependent for burrows, also has a negative impact on Burrowing Owl populations. Where burrowing mammals must be controlled, use nonlethal means (trapping and relocating) whenever possible to obviate the use of strychnine and other chemicals that also kill Burrowing Owls, or use chemical agents known not to result in secondary poisoning.

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.

Loss of native grassland by conversion to agriculture results in loss of foraging and nesting habitat; urbanization also destroys habitat and results in elevated levels of disturbance related to humans (noise, harassment by pets, collisions with vehicles). Maintain a 600 m (approx. 2,000 ft) buffer zone around burrows, and prohibit pesticide applications, rodent control, and other human disturbances within this zone.

Status and Reasons for Concern: This species has a high conservation need locally and throughout its range. The Colorado Division of Wildlife has listed the Burrowing Owl as a Threatened Species. In Physiographic Area 87 the range is restricted, and the subjective evaluation of local birders is that the population has dipped significantly in the past five years. In Physiographic Area 87, BBS data do not show a statistically significant annual rate of change between 1966 and 1996 (P = 0.65, n = 16 routes). Burrowing Owls were present on an average of 2.92% (SE = 1.97) of the BBS routes run in Physiographic Area 87 in Colorado during 1988-1997, at an average abundance of 0.03 (SE = 0.02) individuals per route. The mean number of routes run each year was 11.4 (SE = 1.55). This species is monitored by MCB with nocturnal surveys.

Biological Objective: Maintain or increase the distribution and abundance of Burrowing Owls, based upon results from the BBS and MCB monitoring programs.

Selected References: Andrews and Righter 1992, Haug et al. 1993, Kingery 1998, Pezzolesi 1994.