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Literature Review

Burrowing Owl

Speotyto cunicularia

USFWS: Species of Concern (no official status)
CDFG: Species of Special Concern

Background

Distribution, Abundance and Trends. The Burrowing Owl has a broad distribution that includes open country throughout the Midwest and western United States, Texas and southern Florida, parts of central Canada, and into Mexico and the drier regions of Central and South America. In Southern California, it is known from lowlands over much of the region, particularly in agricultural areas. This species is greatly reduced in numbers throughout its range (DeSante 1991, 1992).

Within the Plan area, burrowing owls are scattered in low numbers on open terrain throughout the lowlands. They occur in open desert areas, in fallow fields, along irrigation dikes and levees, wherever burrows (generally dug by ground squirrels) are available away from intense human activity. They can occur adjacent to residential development, as evidenced by regular observations of these owls in sandy substrates along Washington Avenue in Bermuda Dunes (prior to development of empty lots) (C. Barrows pers. comm.), and around the Palm Springs Airport (Cornett, pers. comm.).

Burrowing owls are notably common in Imperial County along roads and levees in the agricultural areas. They may occur along roads and levees in agricultural areas at the eastern end of the Coachella Valley, within the Plan area. However, our efforts to locate reliable records for burrowing owls in these agricultural areas met with limited success. Biologists from the California Department of Fish and Game (Keeney, pers. comm.) and Coachella Valley Water District who routinely visit the agricultural drains and associated levees around the Salton Sea reported only one burrowing owl observation (Thiery, pers. comm.).

An influx of wintering burrowing owls may occur in the Coachella Valley. The known location information for this species does not allow a determination of wintering birds as the month of observation is not consistently reported; four of the known locations report only the year of observation. Of the 40 known locations, four are listed as observations during the winter months (December to February). The remaining known locations are from observations in the spring and summer months, which probably indicate resident birds, potentially on breeding territories.

Burrowing owls occupy burrows dug by others, primarily ground squirrels. If left undisturbed, they will use the same burrow year after year for nesting. A clutch of 7 to 9 eggs is laid between March and July. Both parents take part in incubation for about 28 days. The young emerge from the nest and spend daylight hours at the burrow entrance with one or both adults. Their distress call is a low rattle, said to be a mimic of a rattlesnake. The burrows selected by these owls are typically abandoned rodent burrows, however, they also commonly use old pipes, culverts or other debris that simulates a hole in the ground.

Burrowing owls follow a crepuscular habit, being most active during the early morning and evening hours. Their diet is predominantly large insects and small rodents, but they will also take small birds, reptiles, amphibians, fish, scorpions, and other available prey. They are often observed perched on fence posts or utility wires. They typically live 8 years or more.

Threats and Limiting Factors. The most significant threat to the continued persistence of the burrowing owl is destruction of habitat. Their ground nesting habit also leaves them susceptible to predation by domestic cats and dogs. Individuals may be killed on roadways while foraging at night. In agricultural areas, levees and irrigation dikes where rodent burrows are present can provide a suitable nest site. In these areas, burrowing owls can be threatened by disturbance as a result of maintenance activities along dikes and levees and by poisoning from pesticide use or rodent poisoning campaigns. Off-road vehicle activity is a threat to the habitat of this species as their burrows can be crushed and their nest sites disturbed. Illegal trash dumping has also been observed to impact burrowing owls (Corey pers. comm..).

Special Considerations. The open burrows on the ground occupied by burrowing owls make them particularly exposed and vulnerable to predation by domestic pets and to disturbance from human activities. Protection of this species should necessarily include protection and maintenance of burrowing mammal populations.