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HABITAT SUITABILITY INDEX MODELS:
nO.82Fish and Wildlife Service
u.s. Department of the Interior
MODEL EVALUATION FORMHabitat models are designed for a wide variety of planning applications where habitat information is an important consideration in the decision process. However, it is impossible to develop a model that performs equally well in all situations. Assistance from users and researchers is an important part of the model improvement process. Each model is published individually to facilitate updating and reprinting as new information becomes available. User feedback on model performance will assist in improving habitat models for future applications. Please complete this form following application or review of the model. Feel free to include additional information that may be of use to either a model developer or model user. We also would appreciate information on model testing, modification, and application, as well as copies of modified
models or test results. Please return this form to:
Habitat Evaluation Procedures Group U.S. Fish and Wildlife Service 2627 Redwing Road, Creekside One Fort Collins, CO 80526-2899 Thank you for your assistance.
Geographic Species Location Habitat or Cover Type(s) Type of Application: Impact Analysis Management Action Analysis Baseline Other Variables Measured or Evaluated Was the species information useful and accurate? Yes No If not, what corrections or improvements are needed? - - - - - - - - - - r: ~/..;'
/".1 • (I ',;
Were the variables and curves clearly defined and useful? Yes No If not, how were or could they be improved?
Were the techniques suggested for collection of field data:
Appropriate? Yes No Clearly defined? Yes No Easily applied? Yes No If not, what other data collection techniques are needed?
Other suggestions for modification or improvement (attach curves, equations, graphs, or other appropriate information)
Additional references or information that should be included in the model:
This document is part of the Habitat Suitability Index (HSI) model series [Biological Report 82(10)J, which provides habitat information useful for impact assessment and habitat management. Several types of habitat information are provided. The Habitat Use Information section is largely constrained to those data that can be used to derive quantitative relationships between key environmental variables and habitat suitability. This information provides the foundation for the HSI model and may be useful in the development of other models more appropriate to specific assessment or evaluation needs.
The HSI Model section documents the habitat model and includes information pertinent to its application. The model synthesizes the habitat use informat ion into a framework appropri ate for fi e 1d app 1 i cat i on and is scaled to produce an index value between 0.0 (unsuitable habitat) and 1.0 (optimum habitat). The HSI Model section includes information about the geographic range and seasonal appl ication of the model, its current verification status, and a list of the model variables with recommended measurement techniques for each variable.
The model is a formalized synthesis of biological and habitat information published in the scientific literature and may include unpublished information reflecting the opinions of identified experts. Habitat information about wi 1dl i fe speci es frequently is represented by scattered data sets co 11 ected during different seasons and years and from different sites throughout the range of a species. The model presents this broad data base in a formal, logical, and simplified manner. The assumptions necessary for organizing and synthesizing the species-habitat information into the model are discussed.
The model should be regarded as a hypothesis of species-habitat relationships and not as a statement of proven cause and effect relationships. The model may have merit in planning wildlife habitat research studies about a species, as well as in providing an estimate of the relative suitability of habitat for that species. User feedback concerning model improvements and other suggestions that may increase the utility and effectiveness of this habitat-based approach to fish and wildlife planning are encouraged. Please send suggestions
Resource Evaluation and Modeling Section National Ecology Center U.S. Fish and Wildlife Service 2627 Redwing Road Ft. Collins, CO 80526-2899
This HSI model was initiated in two modeling workshops hosted by the U.S.
Fish and Wildlife Services ' Gloucester Point, VA, and Lafayette, LA, Field Offices of the Division of Ecological Services. Participants in the Virginia workshop included: Karen Mayne and Gary Fraser, Division of Ecological Services, Gloucester Point, VA; Deborah Rudis, Susanne Nair, and Charlie Rewa, Division of Ecological Services, Annapolis, MD; Bob Hume and Doug Davis, U.S.
Army Corps of Engineers, Norfolk, VA; John Badin, U.S. Army Corps of Engineers, Wilmington, NC; and Charlie Rhodes, U.S. Environmental Protection Agency, Philadelphia, PA. Participants in the Lafayette workshop included the following Division of Ecological Services biologists: Robert Strader, Lafayette, LA; Danny Dunn, Daphne, AL; Robert Willis, Cookeville, TN; and Robert Barkley, Steve Forsythe, and Charles McCabe, Vicksburg, MS. Brian Cade, Patrick Sousa, and the author, U.S. Fish and Wildlife Service, Fort Collins, CO, served as facilitators of the workshops.
Subsequent to the workshops, reviews of the draft model were provided by Robert Barkley, Steve Forsythe, Charles McCabe, Robert Strader, and Robert Willis. The time and contributions of these individuals are sincerely appreciated.
The revised draft was reviewed by Dr. Mark R. Fuller, U.S. Fish and Wildlife Service, Patuxent Wildlife Research Center, Laurel, MD; Mr. Tom Hamer, U.S. Forest Service, Sedro Woolley, WA; and Dr. Jerome A. Jackson, Mississippi State University, Mississippi State. The additional information provided, as well as the time and willingness of these individuals to contribute to the improvement and completion of this model, is gratefully acknowledged.
The cover of this document was illustrated by Jennifer Shoemaker. Word processing was provided by Dora Ibarra. Kay Lindgren assisted with literature searches and information acquisition.
HABITAT USE INFORMATIONGeneral The barred owl (Strix varia) is widely distributed throughout North America, ranging from the east coast to western Canadian Provinces (American Ornithologists' Union 1983). The species has recently expanded its range into extreme western Canada and the northwest United States (Fyfe 1976; Taylor and Forsman 1976; Boxall and Stepney 1982; Marks et al. 1984). In the midwestern and eastern portions of North America the species is associated primarily with mixed woodland, boreal forest, mixed transitional forest, and deciduous forest (Boxall and Stepney 1982). For successful inhabitation the species requires an expansive forested area that contains large mature and decadent trees that provide cavities suitable for security and reproduction.
The diet of the barred owl is governed by availability of prey. The species is primarily nocturnal (Taylor and Forsman 1976), although diurnal foraging and activity is not uncommon (Caldwell 1972; Fuller 1979). Small mammals are the primary component of the barred owls' diet (Wilson 1938;
Earhart and Johnson 1970; Holgersen 1974; Hanebrink et al. 1979). Meadow voles (Microtus pennsylvanicus), short-tailed shrews (Blarina brevicauda), and white-footed mice (Peromyscus leucopus) composed the bulk of the barred owls' prey in Ohio (Dexter 1978). Small mammals accounted for 65.9% of the prey items recorded in Maryland (Devereux and Mosher 1984). Rats, mice (Cricetidae), and shrews (Soricidae) composed 81.5% of the mammalian prey.
Meadow and montane voles (M. montanus) composed 96.3% of the total winter food of barred owls in Montana (Marks et al. 1984).
Fish, amphibians, reptiles, birds, and invertebrates generally account for a smaller portion of the barred owls' diet (Earhart and Johnson 1970).
Birds and arthropods accounted for 14.6% and 19.5%, respectively, of the total number of prey items consumed by barred owls in Maryland (Devereux and Mosher 1984). Investigations in Mississippi, however, suggest that invertebrates, primarily crayfish, exceed small mammals in importance in the barred owls' diet (J.A. Jackson, Department of Biological Sciences, Mississippi State University, Mississippi State; letter dated June 23, 1987).
Information pertaining to dietary water requirements of barred owls was not located in the literature.
Much of the earlier literature pertaining to barred owl ecology (Carter 1925; Errington and McDonald 1937; Bent 1938; Applegate 1975; Soucy 1976) concluded or implied that barred owls prefer to establish nests in close associ at i on with water or withi n forested wet 1and cover types. More recent and exhaustive investigations tend to disprove the conclusion that the species prefers to nest in close proximity to water. Devereux and Mosher (1984) did not record differences in the di stance to water from nest sites and random sample plots in Maryland. Furthermore, radiotelemetry investigations (Nicholls and Warner 1972; Fuller 1979) have shown that barred owls consistently used suitable upland forest cover types more frequently than forested wetlands and lowlands. Devereux and Mosher (1984) concluded that the relationship between barred owls and forested wetland cover types was a result of the vegetation associated with these cover types rather than an attraction for the water itself. Forested wetlands are often inaccessible or too wet for timber harvesting. As a result, these sites often contain remnant stands of mature and old-growth forest. The large size classes and decadent nature of these forests provide ideal cover and nest cavities, thereby attracting and supporting barred owl populations.
Fifty-five percent of barred owl observations in the Pacific Northwest have been reported near a wetland cover type (T. Hamer, U.S. Forest Service, Sedro Woolley, WA; unpubl.). The apparent relationship between barred owls and wetlands may stem from past forest management in the region (Hamer, pers.
comm.). In the Pacific Northwest, low elevation forests historically have been those initially subjected to timber harvest and management. Low elevation areas in this region contain a greater abundance and distribution of wetlands than do tracts of higher elevation and steeper topography. Older seral vegetation stages now occur in these areas, resulting in mixed coniferous and deciduous stands that provide suitable barred owl habitat, frequently in relatively close proximity to wetlands.
The survival of the barred owl depends on the availability of suitable food and forested areas that provide adequate conditions for perching, courtship, and reproduction (Nicholls and Warner 1972; Elody and Sloan 1985).
Barred owls appear to prefer older stands, but earlier stages of forest succession will be used if a suitable number of large diameter trees or snags is present (Hamer, pers. comm.). Although barred owls occasionally may be found in small woodlots, they are much more likely to inhabit extensive tracts of forest (Jackson, unpubl.). The barred owl is most frequently associated with densely forested woodlands and deciduous and mixed deciduous/coniferous forests (American Ornithologists ' Union 1983); however, barred owls are not restricted to specific floristic associations in their foraging activities (Fuller 1979). Deciduous woodlands, specifically riparian and lowland areas, were the most frequently recorded forest types for barred owl nesting throughout North America (Apfelbaum and Seelbach 1983). Establishment of nests in pure coniferous cover types has not been recorded in the midwest and has been recorded only infrequently elsewhere in North America.
Definite preferences for specific cover types were exhibited by barred owls in Minnesota (Nicholls and Warner 1972). Cover types in order of preference were (1) oak (Quercus spp.) woodland, (2) mixed deciduous/coniferous woodland, (3) white cedar (Thuja occidental is) swamps, (4) oak savanna, (5) alder (Alnus spp.) swamps,-Wmarshes, and (7) old fields. Oak woodland and mixed deciduous/coniferous cover types contained trees that provided perch sites and cavities and cover for prey species. The first four cover types were normally free of dense understory vegetation, that might have facilitated foraging through increased visibility and reduced obstructions to flight.