Athene

Abstract: The Burrowing Owl, Speotyto cunicularia hypugaea, is a common resident throughout much of arid North America. The conspicuous diurnal activity of these owls, in combination with their fossorial habits, has attracted the attention of many observers since the middle of the nineteenth century. Yet the accumulated knowledge of the biology of this species is surprisingly sparse, and widely scattered. Bent (1938) assembled most of the basic information to date concerning the life history and biology of Burrowing Owls. The only detailed study available for any New World species of small owl (Ligon 1968) presents a contrast of adaptive patterns to hot, arid environments between Burrowing Owls and Elf Owls (Micrathene whitneyi) and has provided a point of departure for this presentation.

Abstract: We studied the breeding ecology of burrowing owls (Athene cunicularia) in central Saskatchewan during 1982-83. We determined home range, activity patterns, and habitat used for foraging for 6 radiotagged adult male owls. Owls used grass-forb areas for foraging and avoided croplands and grazed pasture. Mean home-range size was 2.41 km2 (range = 0.14-4.81 km2). Peak foraging activity occurred between 2030 and 0630 hours. Ninety-five percent of all movements were within 600 m of the nest burrows. The nesting habitat requirements of short grass, open sites, and burrow availability can be met by managing and protecting existing historic sites. J. WILDL. MANAGE. 54(1):27-35 The burrowing owl is classified as a threatened species in Canada because of an apparent decline of the small breeding population (Wedgwood 1978). In Saskatchewan, the primary breeding range of the burrowing owl in Canada, much of the native habitat originally occupied by burrowing owls has been converted to cropland. Loss of nesting habitat has also been implicated as a leading cause of the population decline in the United States, but the causes appear to be more complex on the Canadian prairies (Wedgwood 1978). As nesting habitat of the burrowing owl declines, it becomes increasingly important to understand the habitat requirements of the species for management and conservation. Many investigators (Coulombe 1971, Thomsen 1971, Martin 1973, Ross 1974, Wedgwood 1976) have documented various aspects of the diurnal activities of burrowing owls during the breeding season. We studied nocturnal movements, acvity patterns, and habitat use of burrowing owls in Saskatchewan with radio telemetry. We thank the World Wildlife Fund, Canada, and the Saskatchewan Department of Parks and R newable Resources for financial support. J. A. King, W. J. Maher, M. R. Duwors, R. J. Smith, D. W. Leach, S. Jana, University of Saskatchewan; J. B. Gollop, Canadian Wildlife Service; SPresent address: 6 Livingston Place, Winnipeg, MB R3T 3T5, Canada. This content downloaded from 207.46.13.25 on Mon, 12 Sep 2016 04:33:22 UTC All use subject to http://about.jstor.org/terms 28 BURROWING OWL MOVEMENTS * Haug and Oliphant J. Wildl. Manage. 54(1):1990 and M. K. Mukerji, Agriculture Canada contributed time and effort to the project. J. B. Gollop and J. A. Wedgwood provided the historical locations of burrowing owl nest sites across Saskatchewan. A special thanks goes to the Deschamps, the Thompsons, and the many farmers who allowed access to their land and provided encouragement during the field work. We also acknowledge A. B. Didiuk, who worked long hours in the field and edited many manuscripts.

Abstract: Terrestrial vertebrates exhibit dynamic, positive interactions that form and dissolve under different circumstances, usually with multiple species as participants. Ecosystem engineers are important facilitators of other species because they cause physical changes in the environment that alter resource availability. Although a species can be associated with more than one partner, facilitators may not be interchangeable if they differ in abundance, behavioral characteristics, or interactions with other factors in ways that condition the outcome of the association. We examined interactions between burrowing owls (Athene cunicularia) and two burrowing mammals, hairy armadillos (Chaetophractus villosus) and plains vizcachas (Lagostomus maximus), and determined whether these ecosystem engineers are interchangeable for owls. We examined reproductive success for owls nesting in these mammal burrows, constructed a logistic regression model to identify habitat characteristics associated with owl nests, and examined the engineering activities of the mammals. Data on reproduction and habitat indicate that armadillos and vizcachas are not interchangeable for owls. Thirty-five percent of the nests in vizcacha burrows produced fledglings; no fledglings were produced from nests outside vizcachas colonies, even though owls nest successfully in armadillo burrows in other parts of Argentina. Vizcachas facilitate burrowing owls by construction of burrows and by producing open understory vegetation through herbivory. In contrast, armadillos do not alter vegetation, and their burrows are suitable for nest sites only when they occur in recently burned areas or areas maintained by anthropogenic disturbance. Our habitat model also suggests that fire plays a key role in maintaining owl populations because fire is the only natural process that reduces shrubs to the level required by owls. Current management practices of eradication of vizcachas and fire suppression in shrublands could have strong negative consequences for burrowing owls.