Habitat selection by northern spotted owls : The consequences of prey selection and distribution

We tested three predictions of a hypothesis that states Northern Spotted Owls (Strix occidentalis caurina) select habitat according to the distribution of their primary prey. Our predictions were that Northern Spotted Owls should (1) select larger (> 100 g) species among the assemblage of available prey, (2) select habitats according to the distribution of large prey, and (3) the owl's reproductive success should be influenced by the availability of large prey. We also evaluated the potential energetic value of several prey species. We found that Northern Spotted Owls (n = 11 pairs and 1 single male) in northwestern California differentially selected the dusky-footed woodrat (Neotoma fuscipes), a moderately large sigmodontine rodent (x mass = 232 g). When foraging, owls selected late seral forest edge sites where dusky-footed woodrats were more abundant. Although the relationship between site selection, prey abundance, and the owl's breeding success was not statistically significant, the average abundance of dusky-footed woodrats at sites foraged by breeding owls (x = 11.4 woodrats 100-trap-nights -1 ) was greater than at sites foraged by nonbreeding owls (x = 4.7 woodrats 100-trap-nights -1 ). We estimated that a male Spotted Owl would require 150,015 to 336,232 kJ over a 153-day period while helping to produce one young, and concluded that the selection of woodrats provided a potential energetic benefit over the use of other prey. These findings provide a partial explanation for the owl's affinity for late seral forests.

[1]  B. Noon,et al.  Between-habitat movement of dusky-footed woodrats and vulnerability to predation , 1997 .

[2]  Len Thomas,et al.  Retrospective Power Analysis , 1997 .

[3]  K. White.  Comparison of fledging success and sizes of prey consumed by spotted owls in northwestern California , 1996 .

[4]  B. Noon,et al.  Demographic characteristics and trends of northern spotted owl populations in northwestern California , 1996 .

[5]  B. Noon,et al.  Use, interpretation, and implications of demographic analyses of northern spotted owl populations , 1996 .

[6]  J. Bart.  Amount of Suitable Habitat and Viability of Northern Spotted Owls , 1995 .

[7]  L. Irwin,et al.  Within-stand nest site selection by spotted owls in the eastern Washington Cascades , 1995 .

[8]  C. J. Zabel,et al.  Influence of primary prey on home-range size and habitat-use patterns of northern spotted owls (Strix occidentalis caurina) , 1995 .

[9]  B. Manly,et al.  Resource selection by animals: statistical design and analysis for field studies. , 1994 .

[10]  B. Noon,et al.  Dusky-footed woodrat abundance in different-aged forests in northwestern California , 1993 .

[11]  R. Balda,et al.  Metabolic rate and evaporative water loss of Mexican Spotted and Great Horned Owls , 1993 .

[12]  B. Biswell,et al.  Northern Spotted Owls: Influence of Prey Base and Landscape Character , 1992 .

[13]  Alan B. Franklin,et al.  Spotted owl roost and nest site selection in northwestern California , 1992 .

[14]  R. J. Gutiérrez,et al.  The California spotted owl: General biology and ecological relations , 1992 .

[15]  L. Ruggiero,et al.  Wildlife and Vegetation of Unmanaged Douglas-Fir Forests , 1992 .

[16]  B. Biswell,et al.  Methods for measuring populations of arboreal rodents. , 1991 .

[17]  B. B. Bingham,et al.  Distinctive features and definitions of young, mature, and old-growth Douglas-fir/hardwood forests , 1991 .

[18]  R. J. Gutiérrez,et al.  Summer habitat ecology of Northern Spotted Owls in northwestern California , 1990 .

[19]  A. T. Doyle.  Use of Riparian and Upland Habitats by Small Mammals , 1990 .

[20]  S. Boutin.  Food supplementation experiments with terrestrial vertebrates: patterns, problems, and the future , 1990 .

[21]  A. B. Carey,et al.  Spotted owl home range and habitat use in southern Oregon coast ranges , 1990 .

[22]  Burt P. Kotler.  The effects of morphology and body size on rates of owl predation on desert rodents. , 1988 .

[23]  S. H. Jenkins,et al.  Sex and age affect vulnerability of desert rodents to owl predation , 1987 .

[24]  M. V. Stalmaster.  The Bald Eagle , 1987 .

[25]  J. R. Murphy,et al.  REPORT OF THE SCIENTIFIC ADVISORY PANEL ON THE SPOTTED OWL , 1987 .

[26]  C. Barrows.  DIET SHIFTS IN BREEDING AND NONBREEDING SPOTTED OWLS , 1987 .

[27]  R. J. Gutiérrez,et al.  Ecology and management of the spotted owl in the Pacific Northwest. , 1985 .

[28]  R. J. Gutiérrez.  An overview of recent research on the spotted owl , 1985 .

[29]  H. Wijnandts,et al.  Ecological Energetics of the Long-Eared Owl (Asio Otus) , 1984 .

[30]  B. V. Horne,et al.  DENSITY AS A MISLEADING INDICATOR OF HABITAT QUALITY , 1983 .

[31]  G. Walsberg.  Chapter 3 – AVIAN ECOLOGICAL ENERGETICS , 1983 .

[32]  H. Southern,et al.  Owls of Europe , 1983 .

[33]  Douglas H. Johnson.  THE COMPARISON OF USAGE AND AVAILABILITY MEASUREMENTS FOR EVALUATING RESOURCE PREFERENCE , 1980 .

[34]  Joseph Tucker Springer,et al.  Some sources of bias and sampling error in radio triangulation , 1979 .

[35]  David R. Anderson,et al.  Statistical inference from capture data on closed animal populations , 1980 .

[36]  G. Caughley,et al.  Analysis of vertebrate populations , 1977 .

[37]  C. D. Marti.  FEEDING ECOLOGY OF FOUR SYMPATRIC OWLS , 1974 .

[38]  Lewis Nelson,et al.  Correction for Sprung Traps in Catch/Effort Calculations of Trapping Results , 1973 .

[39]  R. Graber.  Food and oxigen consumption in three species of owls (STRIGIDAE) , 1962 .

[40]  Don W. Hayne,et al.  Calculation of Size of Home Range , 1949 .