Speotyto cunicularia
The Burrowing Owl is the only owl active both day and night. It is closely associated with prairie dogs and other burrowing mammals. In Texas, it’s breeding is mostly restricted to the western part of the state and the Panhandle area. Texas hosts year-round residents and winter migrants, enabling birders to readily find loose colonies of this long-legged owl throughout the year in all but the northeastern part of the state.
The combination of year-round residency, pair bonding by non-migratory birds that lasts a year (Haug et al.1993) and the year-round use of the nesting burrows can make interpretation of possible and probable TBBA evidence difficult for participants. Although historical records indicate breeding occurred east of Fort Worth and as far southeast as Kleberg County (Oberholser, 1974), only one probable breeding record was from outside western Texas.
DISTRIBUTION: TBBA data indicate the Burrowing Owl breeds almost exclusively in the Trans-Pecos, Rolling Plains and High Plains (Panhandle) ecological regions. The largest concentration of confirmed breeding was in the High Plains.
SEASONAL OCCURRENCE The Burrowing Owl’s habit of using nesting burrows year-round, underground nests, and the presence of both resident and migratory birds made assignment of breeding categories difficult for TBBA observers during the 1987-1992 field work period. In spite of this 47%) of records were confirmed. Just over half (53%) of the confirmed sightings involved seeing recently fledged young, and 34% were adults seen entering or leaving the nests. Of the probable sightings (23% of the records), over half (54.) were pairs seen, and 25% were visits to probable nest sites. All of the possible sightings were birds seen in breeding habitat. With the breeding season from early April to late July (Oberholser, 1974), and migrants, some of them paired, present until mid-April with an extreme late date of May 27 (Oberholser 1974), atlasers had to be cautious about interpreting their data. Oberholser (1974) noted that the early and late dates for eggs are April 13 and May 18, respectively. TBBA data recorded only one nest with eggs at latilong 36100, Quad A3. This nest, containing 4-5 eggs, was recorded on June 30, 1987. This is later than Oberholser indicated for egg laying, and, given the 28-30 day incubation period (Haug et al. 1993), indicates a later egg laying date. The two TBBA records of nests with young occurred on May 29, 1987 and June 7, 1990, at latilong/quad 32102/Al and 34102/B2 respectively. Young are known to move among nest burrows when 10 days old (Henny and Blus 1991) and emerge at about 2 weeks of age (Haug et al. 1993).
BREEDING HABITAT: Burrowing Owls seek expanses of treeless, short-grass plains and prairies, ideally unbroken by cultivation (Oberholser 1974), frequently nesting in loose colonies. Although most often associated with prairie dog towns. Burrowing Owls have been recorded using vacated ground squirrel holes (which they must enlarge) and burrows of rabbits, armadillos, badgers, skunks, foxes, coyotes (Oberholser 1974) and kangaroo rats (Haug et al. 1993). Western Burrowing Owls (Speotyto cunicularia hypugaea) nest in prairies, plains and stony mesas (Oberholser 1974) and can excavate holes where burrowing mammals are absent (Thomsen 1971) but rarely do so. Burrowing Owls alsoaccept artificial nest burrows (Henny and Blus 1981).
Burrowing Owls continue to maintain their burrow throughout most of the breeding season and will reuse it the following year. Non-migratory populations (in Florida) will use and maintain the burrows year-round, using them to avoid avian predation in the winter (Millsap 1992).
Although it is not clear which of the pair selects the burrow, both male and female renovate and maintain burrows by digging. All nest burrows have one or more turns and a mounded entrance, but the depth, size and convolutions depend on the animal that originally dug the burrow. The burrow may be as long as 3 m (10 ft), terminating in a chamber lined with bits of dry animal dung, grass, forb stalks, and feathers (Oberholser, 1974). The nest cup is lined with grass, a few feathers, plant stalks, and rubbish (Oberholser, 1974). The entrance to the burrow is also lined with dried animal dung, thought to mask the owl’s scent (Green, 1983). The entrance is often adorned with highly visible objects–shells, shredded paper, tin foil, cigarette butts, plastic (Millsap 1992).
STATUS: While the confirmed breeding range indicated by TBBA data extends further south and west than reported in Haug et al. (1993) and Johnsgard 1988), it does not support their reported breeding range along the Texas/Oklahoma Red River border east to Grayson County and south to Dallas County. It also shows a reduction in the breeding range reported by Oberholser (1974) as “Common to uncommon on plains of western half south to 30th parallel; rare and highly irregular in remainder of western half, and east locally to Fort Worth, Corsicana (nesting unconfirmed), Austin (at least formerly), and coastal plain from Houston to Kleberg Co.” The only TBBA record (probable, pair seen) outside of western Texas occurred in latilong 30097 quad F4. While Oberholser recorded only three breeding sites in the Trans-Pecos (El Paso, Presidio and Reeves counties), TBBA records nine confirmed and five probable breeding sightings in the Trans-Pecos. In the High Plains and Rolling Plains, TBBA data increases confirmed breeding sightings from Oberholser’s eight to 59.
While the TBBA data indicate more breeding sites than formerly recorded, as a whole,for the Burrowing Owl. North American Breeding Bird Survey data for Texas from 30 routes show a statistically significant -6.9% population change per year for the period 1980-2005. This compares to a survey-wide less significant trend from 277 routes of +2.4% for the same period. In the Rolling Plains south of the Red River survey observers detected an average of 3-10 owls per 40 km (25 mi) route (Sauer et al. 2005). The Texas trend is alarming for the future of this owl in this state. Lockwood and Freeman (2004) attribute this decline to conversion of prairie habitats to agricultural use and population decline of the black-tailed prairie dog.
Text by Sandra Skrei (Postedwith updates 2006)
Literature cited.
Green, G. A. 1983. Ecology of breeding Burrowing Owls in the Columbia basin, Oregon. M. Sc. thesis, Oregon State University, Corvallis.
Haug, E. A., B. A. Millsap, and M. S. Martell. 1993. Burrowing Owl (Speotyto cunicularia) In The birds of North America, No. 60 (A. Poole and F. Gill, eds.) The Birds of North America, Inc., Philadelphia, PA.
Henny, C. J. and L. J. Blus. 1981. Artificial burrows provide new insight into Burrowing Owl nesting biology. Raptor Res. 15: 82-85.
Johnsgard, P. A. 1988. North American owls. Smithsonian Institution, Washington DC.
Lockwood, M. W. and B. Freeman. 2004. The TOS handbook of Texas birds. Texas A&M University Press, College Station.
Millsap, B. A. 1992. Florida Burrowing Owl. In Rare and endangered biota of Florida, vol. 5 Birds. (J. A. Rogers, H. W. Kale II and H. T. Smith, eds.) University Press of Florida, Gainesville.
Oberholser, H. C.. 1974. The bird life of Texas. University of Texas Press; Austin.
Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, results and analysis 1966-2005. Version 6.2 2006. USGS Patuxent Wildlife Research Center, Laurel MD < http://www.mbr-pwrc.usgs.gov/bbs>
Thomsen, L. 1971. Behavior and ecology of Burrowing Owls on the Oakland municipal airport. Condor 73: 177-192.