Flammulated, boreal, and great gray owls in the United States: A technical conservation assessmentAuthor(s): G. D. Hayward; J. Verner
Source: Gen. Tech. Rep. RM-253. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 214 p. 3 Maps.
Publication Series: General Technical Report (GTR)
Station: Rocky Mountain Forest and Range Experiment Station
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DescriptionFlammulated (Otus flammeolus), boreal (Aegolius funereus), and great gray (Strix nebulosa) owls occur over a broad portion of North America and each is designated as a "sensitive species" in four or more USDA Forest Service regions. The insectivorous flammulated owl is a neotropical migrant requiring suitable wintering habitat in the extreme southwestern United States, Mexico, and Central America as well as breeding habitat in the mountains of the western United States. Flammulated owls breed predominantly in yellow-pine (Pinus ponderosa and Pinus jeffreyi) forests and are cavity nesters. The mature and older ponderosa pine forests used as breeding habitat by flammulated owls have changed during the past century due to fire management and timber harvest. In contrast, the boreal owl is a nomadic, small mammal specialist that occurs as an "island" species occupying subalpine and boreal forests. Movements among populations are probably important to boreal owl persistence, and coordinated management of disjunct populations in different Forest Service regions may be important. While the boreal owl's high altitude spruce-fir forests have remained relatively undisturbed in the past, they are coming under increasing harvest pressure as the stock of lower elevation older stands are depleted or reserved. Great gray owls in the western United States occur in mid to high elevation conifer forests. These owls usually nest in mature and older forest stands using existing raptor nests or tops of broken trees and snags for a nest platform. The species' requirement of a secure nesting platform leads to one potential ecological limitation on population size. Prey availability is the other factor thought to limit populations. Flammulated and boreal owls may face significant conservation problems in the absence of conservation planning. Both owls are associated with older forest habitats. Limited research on these species indicates that their demography and life history coupled with their fairly narrow habitat associations make them vulnerable to habitat change. Current forest management practices in many areas (i.e., stand replacement systems) remove quality habitat for these species. Therefore, on at least a local basis, persistence of these species could be in jeopardy, even in the short term. Long-term concerns are greater because the habitats that seem most important to these species require one to two centuries to regenerate. Furthermore, the population biology of both species necessitates across-region planning to facilitate effective conservation planning. Based on limited information, the persistence of great gray owl populations in the United States over both the short and long-term is more certain. Great gray owl foraging habitat use is more compatible with current forest management practices. Our understanding of the ecology and biology of these three species is not sufficient to produce a conclusive assessment of their conservation status. The enclosed assessments, however, give a sufficiently clear picture of each owl's status and the dynamics of important forest habitats to influence management and research decisions. It is clear that development of conservation strategies would aid management but current knowledge of these species is insufficient to produce such a specific document.
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CitationHayward, G. D.; Verner, J. 1994. Flammulated, boreal, and great gray owls in the United States: A technical conservation assessment. Gen. Tech. Rep. RM-GTR-253. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 214 p. 3 Maps.
Keywordsflammulated owl, boreal owl, great gray owl, Otus flammeolus, Aegolius funereus, Strix nebulosa, habitat relationships, old growth, forest dynamics, ponderosa pine forest, spruce-fir forest, conservation
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