Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. ta? £ ay Ae. United Stats, Bird and Small Mammal Agriculture Forest Sens Populations in a Grazed Intermountain Research Station and Ung razed Riparian Research Paper NT-425 cee Habitat in Idaho Dean E. Medin Warren P. Clary THE AUTHORS DEAN E. MEDIN is a research wildlife biologist with the Intermountain Research Station at the Forestry Sciences Laboratory in Boise, ID. He earned a B.S. degree in forest management from Colorado State University in 1957, an M.S. degree in wildlife management from Colorado State University in 1959, and a Ph.D. degree in range ecosystems from Colorado State University in 1976. His research has included studies in mule deer ecology, big-game range im- provement, mule deer population modeling, and nongame bird and small mammal ecology and habitat management. WARREN P. CLARY is project leader of the Intermountain Station’s Riparian-Stream Ecology and Management re- search work unit at Boise, ID. He received a B.S. degree in agriculture from the University of Nebraska and an M.S. degree in range management and a Ph.D. degree in botany (plant ecology) from Colorado State University. He joined the Forest Service in 1960 and has conducted research on forested and nonforested rangelands in Arizona, Louisiana, Utah, Idaho, Oregon, and Nevada. ACKNOWLEDGMENTS We gratefully acknowledge the field and office assistance of John W. Kinney, Sherri A. Brown, Justine L. Wirch, and Patrick V. Turner. Craig R. Contor designed the cover illustration. RESEARCH SUMMARY We compared breeding bird and small mammal popula- tions between a riparian habitat seasonally grazed by cattle and a comparable adjacent riparian habitat protected from grazing for the previous 14 years by a fenced exclosure. The 122-ha exclosure, constructed in 1975, straddles Summit Creek in east-central Idaho. Bird populations were assessed by spot-mapping methods in the spring of 1989. Small mammal populations were compared by removal trapping in late summer of both 1988 and 1989. There was little difference between grazed and ungrazed habitats in total breeding bird density. But total bird biomass, bird species richness, and bird species diversity were 1.87, 1.75, and 1.62 times higher, respectively, in the grazed habi- tat. The differences were almost entirely due to the presence of shorebirds—killdeer, willets, and long-billed curlews—as breeders only on the grazed area. Those species are fre- quently associated with the low vegetational profiles of grazed habitats. Other species, including savannah spar- rows and red-winged blackbirds, were more numerous in the ungrazed habitat. Small mammal populations were almost a third higher on the grazed area than on the ungrazed area. Conversely, both species richness and species diversity of small mammal communities were higher in the ungrazed habitat. Deer mice were the most frequently trapped small mammal on both the grazed and ungrazed areas. They were almost twice as common in the grazed habitat. Montane voles were found in highest densities in the ungrazed habitat. Those two species accounted for 94 percent of the total number of individual animals trapped at Summit Creek. Other species, including vagrant shrews, water shrews, and Great Basin pocket mice, were caught irregularly and in smaller numbers. The use of trade or firm names in this publication is for reader information and does not imply endorsement by the U.S. Department of Agriculture of any product or service. Intermountain Research Station 324 25th Street Ogden, UT 84401 Bird and Small Mammal Populations in a Grazed and Ungrazed Riparian Habitat in Idaho Dean E. Medin Warren P. Clary INTRODUCTION Livestock grazing in riparian ecosystems has been a recent focus of rangeland management in the Western United States (Swanson 1988). Cattle prefer riparian areas for the quality and variety of forage, for easy acces- sibility, for shade, and for a generally reliable source of water (Ames 1977; Gillen and others 1985; Martin 1979). Riparian ecosystems are similarly important to wildlife. Many species of wildlife are either directly dependent on riparian habitats or utilize them more than other habitats (Thomas and others 1979). Several studies have reported adverse effects of cattle grazing on riparian vegetation, and recovery of vegetation when grazing is modified, reduced, or eliminated (Ames 1977; Knopf and Cannon 1982; Rickard and Cushing 1982; Taylor 1986; Winegar 1977). Recovery of riparian vegetation following removal of livestock can be dramatic. If habitat deterioration is not severe, herbaceous vegeta- tion can increase significantly within several growing seasons (Platts and Nelson 1984), and woody vegetation may recover within 5 to 10 years (Rickard and Cushing 1982; Skovlin 1984). But severely deteriorated habitats may require long recovery times, perhaps decades (Knopf and Cannon 1982) or more (Platts and Raleigh 1984). Exclosures, natural areas, and other areas that have received minimal use by livestock are often used as refer- ence areas on rangelands (Kauffman and Krueger 1984; Ohmart and Anderson 1986). Livestock exclosures pro- vide opportunities to study vegetation and associated wildlife communities on ungrazed as compared to grazed habitats. This report compares breeding bird and small mammal populations between a riparian habitat season- ally grazed by cattle and a comparable adjacent riparian area protected from grazing for the previous 14 years by a fenced exclosure. The 122-ha exclosure, constructed in late 1975, is on Summit Creek in east-central Idaho. Bird populations were assessed in the spring of 1989. Small mammal populations were compared by removal trapping during late summer of both 1988 and 1989. Common and scientific names of birds and small mam- mals referred to in this paper are listed in the appendix. STUDY AREA The Summit Creek study area is 41 km north of Mackay in Custer County, ID, at an elevation of about 1,975 m. It is near the southern boundary of the Northern Rocky Mountains physiographic province (Fenneman 1931) in the Little Lost River drainage. Summit Creek originates from springs and flows through a gently sloping, basinlike val- ley bounded on the east by the Lemhi Range and on the west by the Lost River Range. The mountain ranges are rugged and serrated and chiefly composed of limestone, dolomite, quartzite, shale, and schist (Kirkham 1927). Regional climate is semiarid. Average annual precip- itation at Mackay (elevation 1,797 m) is 247 mm, with peaks in May and June. The growing season is short, averaging less than 100 days at Mackay (USDC NOAA 1982). Microrelief in many parts of the riparian area is hummocky, with soils high in total salts (USDA SCS 1987). The riparian zone seldom exceeds 50 to 100 m in width. Several vegetation community types were identified in the riparian area and adjoining upland. For our study, we consolidated the community types into three general categories: sagebrush (Artemisia spp.)/upland, mat muhly (Muhlenbergia richardsonis/hummock, and mesic herba- ceous. The sagebrush/upland type occupies the gentle slopes and terraces adjoining the riparian zone. The other two types—mat muhly/hummock and mesic herbaceous— were considered components of the riparian habitat. Upland vegetation on the site is shrub-steppe (West 1983). The dominant shrubs are low sagebrush (A. arbus- cula) and threetip sagebrush (A. tripartita), with occa- sional individuals of green rabbitbrush (Chrysothamnus viscidiflorus), gray horsebrush (Tetradymia canescens), and big sagebrush (A. tridentata). The herbaceous stra- tum commonly includes Sandberg’s bluegrass (Poa sand- bergii), bluebunch wheatgrass (Agropyron spicatum), aster (Aster spp.), and long-leaf phlox (Phlox longifolia). The hummocky areas are dominated by herbaceous species, most notably mat muhly and thick-spiked wheat-grass (A. dasystachyum), and including Kentucky bluegrass (P. pratensis), tufted hairgrass (Deschampsia cespitosa), short-beaked sedge (Carex simulata), and Kelsey’s phlox (P. kelseyi). The stream is closely bordered by clumped communities of Kentucky bluegrass, beaked sedge (C. ros- trata), and Baltic rush (Juncus balticus). Associated forbs and graminoids include mannagrass (Glyceria spp.), wa- ter sedge (C. aquatilis), Nebraska sedge (C. nebraskensis), American bistort (Polygonum bistortoides), and large- leaved avens (Geum macrophylum). The study area is located largely on public lands ad- ministered by the Bureau of Land Management, US. Department of the Interior. Recent (1976 to 1989) stock- ing levels have varied from about 1,000 to 2,000 animal unit months (AUM’s), with a grazing season from about mid-May to late October (Hale 1989). Stocking levels and grazing periods are adjusted annually on the basis of current resource conditions. METHODS Two 9-ha plots, one in the upper (westernmost) section of the exclosure and the other in the adjacent (upstream) grazed riparian area, were censused for breeding birds using the spot-map method (International Bird Census Committee 1970). Plot locations were selected on the basis of similarities in topography and vegetation between the grazed and ungrazed environments. The census plots, 600 by 150 m, were oriented lengthwise along Summit Creek and gridded with transects crossing the stream channel. Both plots straddled the riparian zone and in- cluded part of the extensive uplands. Grid points were surveyed and marked with numbered stakes at 25-m intervals. Eleven census visits were made to each plot from May 17 to June 29, 1989. The same observer (DEM) conducted the censuses on both plots. Most of the spot- mapping was done from sunrise to early afternoon when birds were most active. Census routes were varied by choosing different routes through the plot, with different starting and ending points. To ensure complete coverage, the plot was censused by walking within 25 m of all points on the grid. Observations and registrations extended well beyond plot boundaries. At the end of the sampling period, clusters of observa- tions and coded activity patterns on species maps were circled as indicating areas of activity or approximate terri- tories (International Bird Census Committee 1970). Frac- tional parts of boundary territories were included. Oelke (1981) summarized methodological difficulties and other special problems of the mapping method. We followed Hill (1973) for estimates of species diversity. A 1.7-ha trapping grid was located in each of the grazed and ungrazed study plots to estimate small mammal populations. Trapping grids were placed near the center of the 9-ha plots established to census bird populations. Each grid measured 225 by 75 m and consisted of 40 trap- ping stations systematically spaced at 25-m intervals in 10 rows and 4 columns. The rectangular grids were posi- tioned lengthwise along Summit Creek and straddled the stream channel. Two Museum Special mouse traps and one Victor rat trap were placed near each trapping sta- tion. Traps were baited with a mixture of peanut butter and rolled oats and examined daily for 5 consecutive days from August 3 to August 7, 1988, and from August 17 to August 21, 1989. Vegetation and other features of the grazed and un- grazed study plots were measured from July 17 to August 30, 1989. Twenty sample locations were established within each of the three plant community types for a total sample size of 60 per study plot. A 50- by 50-cm (0.25-m?) quadrat was located at each of the systematically posi- tioned sample locations. Canopy cover (Daubenmire 1959) was ocularly estimated for the total of each plant life form (graminoid, forb, shrub) and recorded as the midpoint of one of eight percent-cover classes (0-1, 1-5, 5-10, 10-25, 25-50, 50-75, 75-95, 95-100). Percentages of litter, rock, bare ground, and lichen-moss were similarly estimated. The vegetative height (excluding flower and seed-head heights) of each graminoid, forb, and shrub nearest the center of each quadrat was measured. Biomass of graminoids, forbs, and shrubs was deter- mined by clipping vegetation from ground level upward within a vertical projection from the 0.25-m? quadrats. Clipped materials were bagged, ovendried, and weighed. Plant names follow Hitchcock and Cronquist (1973). Bird nomenclature is from the 1983 AOU Check-list (American Ornithologists’ Union 1983). Scientific and common names of mammals follow Jones and others (1986). RESULTS AND DISCUSSION We found structural (physiognomic) differences in the vegetation between grazed and ungrazed habitats on Summit Creek. Those differences were apparently re- flected in the organization of associated breeding bird and small mammal communities. Vegetation The most evident structural difference in the vegetation was in the height values where graminoid, forb, and shrub height means were significantly reduced on the grazed site (table 1). Other differences were primarily in the herbaceous layer where graminoid and forb biomass and graminoid canopy cover values were lower on the grazed site. Graminoid biomass on the grazed plot was only about one-seventh that inside the exclosure. Esti- mates of forb and shrub cover were similar on the grazed and ungrazed areas. There was significantly more rock coverage on the grazed plot. Shrub biomass and shrub, bare ground, and litter coverage were similar. Lichen- moss cover values were slightly higher on the grazed site. There were no tall shrubs or trees on the study plots. Birds We recorded eight species of birds breeding on the Sum- mit Creek study site; seven species bred on the grazed plot and four species bred on the ungrazed plot (table 2). Vesper sparrows, savannah sparrows, and western mead- owlarks were found as breeding birds on both the grazed and ungrazed plots. Killdeer, willets, long-billed curlews, Table 1—Vegetation and other features of grazed and ungrazed study plots, Summit Creek, ID, 1989 Ungrazed Grazed Item Mean’ SD Mean' SD p2 Graminoid Biomass (g/m?) 267.6 254.2 36.7 30.8 <0.01 Canopy cover (%) 61.6 30.5 51.9 30.3 .08 Height (m) 18 09 06 03 <01 Forb Biomass (g/m?) 24.9 29.8 119 146 <.01 Canopy cover (%) 12.0 13.2 115 11.9 81 Height (m) 07 05 .03 02 <.01 Shrub Biomass (g/m?) 71.1 164.5 73:0% .212:7 91 Canopy cover (%) 7.4 145 73 13.9 97 Height (m) 34 .21 .26 ‘12 01 Other Bare ground (%) 20.3 25.0 23.3 24.2 50 Litter (%) 10.4 115 9.1 11.6 55 Rock (%) 64 1.52 2.27 5.89 04 Lichen-moss (%) 30 1.15 84 2.27 10 'n = 60 except for forb and shrub height means for which n ranged from 50 to 58. 2Probability associated with unpaired ttests. P of less than 0.10 was con- sidered significant. and Brewer’s blackbirds were territorial only on the grazed area. Red-winged blackbirds nested only on the ungrazed plot. Wide-ranging raptorial birds, although commonly seen, were not included in the analysis. Transient species were also excluded. Other birds, observed as visitors to the study site, are listed in the appendix. We found little difference between the grazed and un- grazed plots in total breeding bird density (table 2). But estimates of total bird biomass differed markedly on the two plots. Biomass on the grazed plot (226 g/ha) was al- most twice that (121 g/ha) on the ungrazed plot (table 2). The difference in total biomass was almost entirely due to the presence of large shorebirds (killdeer, willet, long- billed curlew) that were breeders only on the grazed plot. Species richness and our estimate of bird species diversity (the reciprocal of Simpson’s index) were larger on the grazed plot, again as a result of the presence of the three shorebirds that established breeding territories only on the grazed plot. Curlew populations are declining in some areas of the Western United States as habitat is lost to agriculture and other land development (Ryser 1985). It is a short-to- midgrass prairie nesting species (Pampush 1980), often nesting in moist meadows near streams and lakes, as well as dry upland habitats (Harrison 1979). Long-billed cur- lews prefer breeding habitats containing short grass, bare ground, shade, and abundant invertebrate prey (Pampush 1980). Livestock grazing tends to maintain the low vegeta- tional profile apparently preferred by curlews as breeding habitat. At Summit Creek, we observed them most often near the stream in mesic herbaceous communities domi- nated by grasses, sedges, and rushes. Killdeer and willets also nest in open habitats where vegetation is sparse and low, usually within short flight distances to feeding areas (Palmer 1967). Both are ground-inhabiting species, building their nests and forag- ing there. We saw willets most often wading in the stream or pecking and probing for insects along the shore- line. Killdeer were usually seen either in flight or on the ground within a few meters of the stream in the most open habitats. Distraction displays and other territorial behaviors exhibited by both the killdeer and willet were noted only on the grazed plot. Taylor (1986) reported a positive response by killdeer to grazing in southeastern Oregon. In North Dakota, killdeer and willets were ob- served in significantly greater densities in grazed habitats (Renken and Dinsmore 1987). Savannah sparrows, numerically dominant on both study plots, were found in greater numbers on the un- grazed plot (table 2). Kantrud (1981) similarly found a negative response by savannah sparrows to grazing in North Dakota native grasslands. A preference of this species for idle or lightly grazed areas was also noted by Owens and Myres (1973). This sparrow frequents open fields and meadows and is most commonly found in moist, grassy habitats in Idaho (Burleigh 1972). It is usually restricted to the vicinity of streams, ponds, lakes, and irrigation systems—often where soils are alkaline (Ryser 1985). Savannah sparrows have an affinity for habitats with a rank growth of vegetation and a dense ground cover (Linsdale 1938), a condition existing in more abun- dance in the ungrazed habitat on the Summit Creek site. Most savannah sparrow territories on the study area were located in the mat muhly/hummock community type al- though other plant communities were often included within territorial boundaries. Table 2—Density (pairs/40 ha), diversity, and other attributes of breeding bird populations on grazed and ungrazed study plots, Summit Creek, ID, 1989 Foraging Nesting Density Species guild' guild? Ungrazed Grazed Killdeer GGI GRN 35. 44 Willet SPI GRN + 3.1 Long-billed curlew GFO GRN + 1.8 Vesper sparrow GFO GRN 8.4 76 Savannah sparrow GFO GRN 39.1 24.9 Red-winged blackbird GFO CRN 12.0 + Western meadowlark GG! GRN 8.0 6.2 Brewer's blackbird GFO GBN + 17.3 Total pairs/40 ha 67.5 65.3 Total individuals/km? 338 327 Biomass‘ (g/ha) 121 226 Species richness (n) 4 7 Species diversity® (1/Zp?) 2.52 4.07 "After DeGraaf and others (1985). GGI = ground gleaning insectivore, SPI = shoreline probing insectivore, GFO = ground foraging omnivore. ?After Harrison (1979). GRN = ground nester, CRN = cattail, rush, sedge, reed, grass, and bush nester, GBN = ground and bush nester. 34 indicates bird observed infrequently (less than three registrations). “Species weights from Dunning (1984). SAfter Hill (1973). Here, p,is the proportional abundance of the n species in a sample. Vesper sparrows and western meadowlarks were both found in similar densities on grazed and ungrazed plots (table 2). Both species mainly frequent grasslands and open, low-growing shrub habitats (Ryser 1985). Both for- age and nest on the ground. At Summit Creek, we found vesper sparrows most often in the sagebrush/upland com- munity type. Western meadowlarks were distributed thoughout the grazed and ungrazed plots. Vesper spar- rows and western meadowlarks were negatively affected by livestock grazing in northern Nevada (Page and others 1978). In North Dakota, western meadowlarks were about equally common under three levels of grazing intensity (Kantrud 1981), and in Oklahoma, Smith (1940) found that only severe overgrazing made conditions unsuitable for the western meadowlark. Red-winged blackbirds were found as breeding birds only on the ungrazed plot (table 2). Conversely, Brewer’s black- birds were territorial only on the grazed plot. Nests of the red-winged blackbird were bound to tall, coarse stalks of beaked sedge found in thick stands near the stream. Heights of beaked sedge communities in the grazed plot were considerably reduced as a result of livestock grazing, thereby essentially eliminating potential nesting habitat for red-winged blackbirds. Nests of Brewer’s blackbirds were on the ground in tussocks of grasses and forbs or beside a clod of dry manure. Taylor (1986) found red- winged blackbirds more abundant in undisturbed or rarely grazed riparian habitats in southeastern Oregon. In North Dakota, Kantrud (1981) found that red-winged blackbird populations were greatly reduced or extirpated by heavy grazing. Small Mammals Six species of small mammals were trapped during two seasons of study at Summit Creek (table 3). Deer mice and montane voles accounted for over 94 percent of 115 individual animals trapped. Each of those species was trapped on both grazed and ungrazed study plots. Other species were caught irregularly and in smaller numbers. Table 3—Relative abundance, naive density, and other attributes of small mammal popula- tions on grazed and ungrazed study plots, Summit Creek, ID, 1988 and 1989 Relative abundance Naive density? Foraging (n/100 trap nights) (n/ha) Species guild’ Ungrazed Grazed Ungrazed Grazed Vagrant shrew INS 1988 0.2 0.0 0.6 0.0 1989 ne) 0 0 0 Water shrew INS 1988 2 0 6 0 1989 3 0 1.2 0 Northern pocket gopher HER 1988 2 0 6 0 1989 0 0 0 0 Great Basin pocket mouse GRA 1988 2 0 6 0 1989 0 0 0 0 Deer mouse OMN 1988 2.7 5.2 9.5 18.3 1989 1.3 48 4.7 17.2 Montane vole HER 1988 1:5 8 5.3 3.0 1989 1.8 0 6.5 0 Total naive density (n/ha) 1988 17.2 21.3 1989 12.4 17.2 Biomass (g/ha) 1988 304 354 1989 283 282 Species richness (n) 1988 6 1989 3 1 Species diversity? (1/2 p?) 1988 2.47 1.31 1989 2.33 1.00 ‘After Martin and others (1951). INS = insectivore, HER = herbivore, GRA = granivore, OMN = omnivore. 2After Wilson and Anderson (1985). Effective trapping area and grid size are assumed to be equal. 2After Hill (1973). Here, p,is the proportional abundance of the n species in asample. Four species—vagrant shrews, water shrews, northern pocket gophers, and Great Basin pocket mice—were trapped only in the ungrazed habitat. In 1989, only the deer mouse was caught on the grazed site. Estimated small mammal density was almost a third higher in the grazed habitat (table 3). Total biomass values, however, were similar between the grazed and ungrazed plots. Also, small mammal species richness and our estimates of small mammal species diversity were larger within the exclosure. Each of the six species recorded during the study was trapped in the ungrazed habitat. Only two species were trapped in the grazed habitat. Deer mice were the most frequently trapped small mammal in both the grazed and ungrazed habitats (table 3). Naive density (Wilson and Anderson 1985) on the grazed plot was more than twice that on the un- grazed plot. Most of the deer mice were trapped in the sagebrush/upland community type that occupied the slopes and terraces adjoining the riparian zone. They were trapped infrequently in mesic herbaceous and mat muhly/hummock communities that made up the riparian habitat. Brown (1967a) also trapped deer mice more com- monly in areas distant from water as compared to those adjacent to water. The deer mouse is one of the most widespread and gen- eralized of all North American rodents (Baker 1968). It is Idaho’s most common mammal (Larrison and Johnson 1981). They are found in diverse habitats including swamps, waterways, forests, grasslands, and deserts, and among rocks and cliffs (Larrison and Johnson 1981). It occupies a variety of plant successional stages (Thomas 1979). Higher densities on the grazed plot at Summit Creek suggest a tolerance by the deer mouse of habitats with a low, sparse herbaceous layer. Samson and others (1988) found deer mice frequently associated with low values of grass and litter cover as well as the presence of shrubs. Others have reported contradictory results when com- paring the abundance of deer mice in grazed versus un- grazed habitats. Kauffman and others (1982) found more deer mice in eastern Oregon riparian habitats after late- season grazing (late August to mid-September) than in ungrazed riparian habitats. But by late summer of the following year, and before grazing, the species composi- tion of small mammal communities was not significantly different between grazed and ungrazed plots. Similarly, Moulton (1978) reported a positive response by deer mice to grazing in a cottonwood (Populus sargentii) riparian habitat in eastern Colorado. Samson and others (1988) also found deer mouse densities consistently higher on grazed pastures. Conversely, Rucks (1978) reported fewer deer mice in grazed versus ungrazed riparian communi- ties. Hanley and Page (1982) found a positive response by deer mice to grazing in mesic habitats and a negative response in dry habitats. Unlike the deer mouse, highest densities of the mon- tane vole occurred in the ungrazed area (table 3). Four times as many montane voles were trapped on the un- grazed plot than on the grazed plot. Most were trapped in streamside habitats with the frequency of capture highest in mesic herbaceous communities. None were trapped in the sagebrush/upland community type. Montane voles occur most commonly in moist, weedy, or brushy areas near water at the edge of grasslands (Larrison and Johnson 1981). The importance of vegetative cover to the montane vole has been well documented (Brown 1967a; O'Farrell and Clark 1986). Grass seems to be a desirable component of the habitat (Randall and Johnson 1979). In eastern Oregon, high pregrazing populations of mon- tane voles were either drastically reduced or eliminated after late-season grazing (Kauffman and others 1982). Vagrant shrews and water shrews, both scarce on the study plots, were trapped only on the ungrazed area (table 3). Captures were irregular and consisted of only one or two animals in each trapping period. All were caught near the stream in mesic herbaceous communities. Vagrant shrews prefer moist, grassy habitats (Spencer and Pettus 1966), but they occur in a variety of other habitats including forests and shrublands (Brown 1967b). Water shrews are typically found along edges of swift- flowing streams with rocks, logs, crevices, and overhang- ing banks (Beneski and Stinson 1987). Kauffman and others (1982) reported reduced populations of the vagrant shrew in postgrazing environments in eastern Oregon. Other species of small mammals were either trapped or observed on the Summit Creek study site. The Great Basin pocket mouse, a species that generally occurs in arid and semiarid habitats (Verts and Kirkland 1988), was trapped only on the ungrazed plot (table 3). It was caught at a single location in the sagebrush/upland com- munity type where giant wildrye (Elymus cinereus) was codominant with scattered individuals of sagebrush and rabbitbrush. Mounds of the northern pocket gopher were evident throughout the area, but it was trapped only in the ungrazed habitat. Columbian ground squirrels (Sper- mophilus columbianus) were occasionally seen on the study area, especially early in the season. Mink (Mustela vison) and muskrats (Ondatra zibethicus) were rarely observed and only in the ungrazed habitat. REFERENCES American Ornithologists’ Union. 1983. Check-list of North American birds. 6th ed. Washington, DC: American Ornithologists’ Union. 877 p. Ames, Charles R. 1977. 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APPENDIX: BIRDS AND MAMMALS OBSERVED ON OR OVER GRAZED AND UNGRAZED STUDY PLOTS, SUMMIT CREEK, ID, 1989 Birds Great blue heron Canada goose Green-winged teal Mallard Northern pintail Cinnamon teal American wigeon Lesser scaup Northern harrier Red-tailed hawk American kestrel Sandhill crane Killdeer Willet Spotted sandpiper Long-billed curlew Wilson’s phalarope Mourning dove Horned lark Violet-green swallow Northern rough-winged swallow Cliff swallow Barn swallow Black-billed magpie Common raven Loggerhead shrike European starling Vesper sparrow Savannah sparrow Red-winged blackbird Western meadowlark Yellow-headed blackbird Brewer’s blackbird Brown-head cowbird Mammals Vagrant shrew Water shrew Columbian ground squirrel Northern pocket gopher Great Basin pocket mouse Deer mouse Montane vole Muskrat Coyote Mink Pronghorn Ardea herodias Branta canadensis Anas crecca Anas platyrhynchos Anas acuta Anas cyanoptera Anas americana Aythya affinis Circus cyaneus Buteo jamaicensis Falco sparverius Grus canadensis Charadrius vociferus Catoptrophorus semipalmatus Actitis macularia Numenius americanus Phalaropus tricolor Zenaida macroura Eremophila alpestris Tachycineta thalassina Stelgidopteryx serripennis Hirundo pyrrhonota Hirundo rustica Pica pica Corvus corax Lanius ludovicianus Sturnus vulgaris Pooecetes gramineus Passerculus sandwichensis Agelaius phoeniceus Sturnella neglecta Xanthocephalus xanthocephalus Euphagus cyanocephalus Molothrus ater Sorex vagrans Sorex palustris Spermophilus columbianus Thomomys talpoides Perognathus parvus Peromyscus maniculatus Microtus montanus Ondatra zibethicus Canis latrans Mustela vison Antilocapra americana Medin, Dean E.; Clary, Warren P. 1990. Bird and small mammal populations in a grazed and ungrazed riparian habitat in Idaho. Res. Pap. INT-425. Ogden, UT: U.S. Depart- ment of Agriculture, Forest Service, Intermountain Research Station. 8 p. There was little difference between grazed and ungrazed habitats in total breeding bird density, but total bird biomass, bird species richness, and bird species diversity were 1.87, 1.75, and 1.62 times higher, respectively, in the grazed habitat. Small mammal populations were almost a third higher on the grazed area than on the ungrazed area. KEYWORDS: density, diversity, biomass, nongame birds, shorebirds, rodents, shrews, rangeland, exclosure INTERMOUNTAIN RESEARCH STATION The Intermountain Research Station provides scientific knowledge and technology to im- prove management, protection, and use of the forests and rangelands of the Intermountain West. Research is designed to meet the needs of National Forest managers, Federal and State agencies, industry, academic institutions, public and private organizations, and individu- als. Results of research are made available through publications, symposia, workshops, training sessions, and personal contacts. The Intermountain Research Station territory includes Montana, Idaho, Utah, Nevada, and western Wyoming. Eighty-five percent of the lands in the Station area, about 231 million acres, are classified as forest or rangeland. They include grasslands, deserts, shrublands, alpine areas, and forests. They provide fiber for forest industries, minerals and fossil fuels for energy and industrial development, water for domestic and industrial consumption, forage for livestock and wildlife, and recreation opportunities for millions of visitors. Several Station units conduct research in additional western States, or have missions that are national or international in scope. Station laboratories are located in: Boise, Idaho Bozeman, Montana (in cooperation with Montana State University) Logan, Utah (in cooperation with Utah State University) Missoula, Montana (in cooperation with the University of Montana) Moscow, Idaho (in cooperation with the University of Idaho) Ogden, Utah Provo, Utah (in cooperation with Brigham Young University) Reno, Nevada (in cooperation with the University of Nevada) USDA policy prohibits discrimination because of race, color, national origin, sex, age, reli- gion, or handicapping condition. Any person who believes he or she has been discriminated against in any USDA-related activity should immediately contact the Secretary of Agriculture, Washington, DC 20250.