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Temporal Variation in Songbird Abundance on Grasslands in Canaan Valley, West Virginia
Kelly A. Chadbourne and James T. Anderson

Southeastern Naturalist, Volume 14, Special Issue 7 (2015): 344–356

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Southeastern Naturalist K.A. Chadbourne and J.T. Anderson 2015 Vol. 14, Special Issue 7 344 Canaan Valley & Environs 2015 Southeastern Naturalist 14(Special Issue 7):344–356 Temporal Variation in Songbird Abundance on Grasslands in Canaan Valley, West Virginia Kelly A. Chadbourne1,2 and James T. Anderson1,* Abstract - Grassland songbirds have been declining due to loss of habitat. In Canaan Valley, WV, grassland habitats primarily consist of active and idle pastures and hayfields. Our objectives were to document the species of breeding birds that occurred on grasslands of the Canaan Valley National Wildlife Refuge and evaluate temporal patterns of abundance among months and years. This study took place on 3 idle hayfields and 3 idle pastures in the Refuge during the summers of 1999 and 2000. At the conclusion of the first field season, half of each field was mowed. A total of 28 species—13 in 1999 and 27 in 2000—was documented. Dolichonyx oryzivorus (Bobolink), Sturnella magna (Eastern Meadowlark), Passerculus sandwichensis (Savannah Sparrow), and Agelaius phoeniceus (Red-winged Blackbird) were dominant. Additional species observed included Ammodramus savannarum (Grasshopper Sparrow) and Circus cyaneus (Northern Harrier). Species diversity, species richness, and total bird abundance varied among months (P < 0.05). Densities were higher in July than in May, June, and August; however, total number of birds peaked later in 1999 than in 2000. Species richness and diversity were lower in August than other months. Temporal variations in grassland bird diversity, richness, and abundance were likely influenced by precipitation patterns and land-use practices on and adjacent to the Refuge. Introduction Populations of North American grassland birds have undergone more consistent and steeper population declines than the birds of other guilds (Jones and Vickery 1997, Kantrud and Higgins 1992, Knopf 1994, Sauer et al. 2012). The North American Breeding Bird Survey indicates that Eremophila alpestris (L.) (Horned Lark), Passerculus sandwichensis (Savannah Sparrow), Ammodramus savannarum (Grasshopper Sparrow), Ammodramus henslowii (Audubon) (Henslow’s Sparrow), Pooecetes gramineus (Vesper Sparrow), Dolichonyx oryzivorus (Bobolink), and Sturnella magna (Eastern Meadowlark) have all undergone significant population declines in the last several decades (Sauer et al. 2012, Wells and Rosenberg 1999). Possible reasons for these reductions include a change in agricultural technology, farmland abandonment, more frequent haycrop rotation, and losses of habitat due to urbanization (Bollinger et al. 1990, Herkert et al. 1996, Jones and Vickery 1997, Norment et al. 1999). In the northeastern US, all of the common grassland bird species are showing long-term decreasing population trends (Sauer et al. 2012; Table 1). 1Wildlife and Fisheries Resources Program, Division of Forestry and Natural Resources, West Virginia University, PO Box 6125, Morgantown, WV 26506. 2Current address - US Fish and Wildlife Service, Great Bay National Wildlife Refuge, 100 Merrimac Drive, Newington, NH 03801. *Corresponding author - jim.anderson@mail.wvu.edu. Southeastern Naturalist K.A. Chadbourne and J.T. Anderson 2015 Vol. 14, Special Issue 7 345 Many grassland bird species require large tracts of grassland and therefore are vulnerable to habitat fragmentation (Norment et al. 1999). In the northeastern US, grasslands have declined >60% since the 1930s (Norment et al. 1999, Vickery et al. 1994). In part, because native grassland habitats have been severely altered by agricultural practices, grasslands are among the continent’s most endangered ecosystems (Vickery et al. 1999). Loss of grasslands has exceeded 80% in most areas, and where land is well suited for agricultural crops, less than 0.1% of native prairie remains (Vickery et al. 1999). However, in the Midwest and northeastern US, agricultural lands have provided adequate breeding habitat for many species, particularly the Bobolink and Eastern Meadowlark (Vickery et al. 1999). Studies of grassland birds in West Virginia have focused on populations living on reclaimed mine sites (Whitmore and Hall 1978); however, studies on grassland birds in the state’s agricultural grasslands have not been conducted. Moreover, survey design, population monitoring, and habitat-use studies need to consider temporal trends in grassland bird populations (George et al. 1992, Ralph and Scott 1981, Sauer and Droege 1990). The objectives of our study were to document which species of breeding birds occurred on the grasslands of the Canaan Valley National Wildlife Refuge (hereafter, the Refuge) and to evaluate temporal patterns of their abundance among months and years. Study Area We conducted this study on the Refuge, which is located in Canaan Valley (hereafter, the Valley), Tucker County, northeastern West Virginia. The Valley, which is 1.9–3.7 miles (3–6 km) wide, 14.9 miles (24 km) long, and oriented on a northeast–southwest axis, sits at an elevation of 3150–324 8 ft (960–990 m) above sea level. Ridges surrounding the Valley rise 1001 feet (305 m) above the Valley’s floor (USFWS 1979). The Valley’s floor hosts a large wetland complex (~6025 ac [2438 ha]) that consists of meadows, bogs, hayfields, beaver ponds, and boreal forests. Table 1. Population trends of grassland birds (% change, 1966–2011) on the Canaan Valley National Wildlife Refuge, Tucker County, WV (Sauer et al. 2012). Total trend = survey-wide grassland bird species group population change; USFWS Region 5 NE) = grassland bird population change data for USFWS refuges in Connecticut, Delaware, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Virginia, and West Virginia; WV = population trend data for grassland birds found on the Canaan Valley National Wildlife Refuge for 1999 and 2000. Species Total trend USFWS Region 5 (NE) WV Savannah Sparrow -0.50 -2.28 -6.84 Bobolink -1.58 +0.15 +2.11 Eastern Meadowlark -2.74 -4.68 -3.40 Red-winged Blackbird -1.04 -2.62 -2.58 Vesper Sparrow -0.76 -5.29 -15.05 Grasshopper Sparrow -3.38 -4.28 -12.00 Northern Harrier -0.63 -3.11 - Southeastern Naturalist K.A. Chadbourne and J.T. Anderson 2015 Vol. 14, Special Issue 7 346 The Valley is characterized by cold winter temperatures and moderate summers. Summer temperatures average 75–79 °F (24–26 °C) during the day and 50–55 °F (10–13 °C) at night (NOAA 1999). Because the climate and vegetation are similar to more northerly regions, many boreal plants are at the southernmost extent of their range in the Valley (Fortney 1993). An annual average of 92 frostfree days extends from 31 May–1 September (Vogelmann 1978). Total average rainfall is nearly 45 in (114 cm) (NOAA 1999). In 1999, the Valley’s total annual rainfall was 37.6 in (95.6 cm), due in part to sub-average rainfall from June to September (Fig. 1). In fact, West Virginia experienced a statewide drought during the summer of 1999. In 2000, the total rainfall of 44.3 in (112.6 cm) was near normal (Fig. 1; NOAA 2000). There were 8.6 in (21.9 cm) more rainfall for May–August during 2000 than in 1999. The history of human intervention in the Valley is discussed by Fortney (1993) and Warren (2001). Although agriculture historically occurred here, it never flourished. Nonetheless, some farms still exist. Many crops did not produce well because of the short growing season, so after the area was logged, cattle became the predominant agricultural product (USFWS 1979). Pastures and hayfields are found in the slightly drier southern part of the Valley. The Refuge’s grasslands consist of dry upland areas, Crataegus spp. (hawthorn) savannahs, saturated wet meadows, and saturated scrub-shrub wetlands, which Vickery et al. (1999) include in the broad definition of grassland systems. Methods Experimental design We conducted this study on 6 grassland fields—designated as the Beall, Cortland, Freeland, Harper, Herz, and Thompson tracts—that total 730 ac (295 ha) Figure 1. Monthly precipitation totals (cm) for 1999–2000, and normal monthly rainfall values for Canaan Valley, Tucker County, WV 1999–2000. Southeastern Naturalist K.A. Chadbourne and J.T. Anderson 2015 Vol. 14, Special Issue 7 347 (mean = 121.6 ac/field, SE = 31.4 [49.2 ha/field, SE = 12.7]). We classified each plot according to its prior land use as (a) idle hayfield (Beall [230 ac (93 ha)], Harper [180 ac (73 ha)], and Thompson [59 ac (24 ha)]) or (b) idle pasture (Cortland [40 ac (16 ha)], Freeland [69 ac (28 ha)], and Herz [151 ac (61 ha)]). At the end of the 1999 breeding season in late August, 50% of the grassland portions of Beall, Cortland, Freeland, Harper, and Thompson were randomly chosen and 1 large block was mowed to determine the effects of habitat manipulation on breeding bird success (Warren 2001). The Herz idle pasture was not mowed because it was too wet. We established transects along the length of each field for bird and vegetation surveys. We located transects 164 ft (50 m) away from field edges to facilitate bird counts. Breeding bird counts To estimate breeding bird densities, we conducted strip-transect surveys (Best et al. 1997, Franzreb 1981). We conducted 13 weekly bird counts using one person on each field from May to August 1999–2000. We conducted weekly surveys within 5 hours of sunrise, recording all birds seen or heard within 164 ft (50 m) of the transect center, which provided a transect width of 328 ft (100 m) (Best et al. 1997, Gates 1995). The edges of the strip tansects were flagged to facilitate complete survey coverage. We did not conduct counts when it was raining or when wind speeds exceeded 10 mi (16 km) per hour (Best et al. 1997). As part of another study (Warren 2001), we recorded bird species, gender, and behavior (e.g., singing, calling) when possible. We tried to walk the transects at a pace that was slow enough to count all individuals but fast enough to avoid double-counting individuals (Best et al. 1997). As a further check against double-counting birds, we excluded individuals that flew overhead and did not alight within our study fields (Best et al. 1997). Statistical analyses We calculated the average density (number of birds/ac [number of birds/ha]) for each month at each field. We also analyzed total birds and 3 target species— Bobolink, Savannah Sparrow, and Eastern Meadowlark—to determine overall differences in months and years for total bird and target-species densities. We chose these 3 species because they occurred on both habitat types (pastures and hayfields) during both years and because their populations are declining. We calculated species diversity, specifically the Shannon-Weiner diversity index, using the maximum number of individuals of a species observed on a field during each month (Shannon 1948, Zar 1999). We calculated species richness by determining the number of species found on each field during the month and standardized them by field size. We checked data for normality using the Shapiro-Wilk statistic and for homogeneity of variances by plotting residuals (Cody and Smith 1991). Because the assumptions for parametric tests were not met (Conover and Iman 1981), we rank-transformed density, richness, and diversity data. We used 3-way analysis of variance (ANOVA) to compare density, richness, and diversity (dependent Southeastern Naturalist K.A. Chadbourne and J.T. Anderson 2015 Vol. 14, Special Issue 7 348 variables) among months (May, June, July, and August), years (1999 and 2000), habitat types (pastures and hayfields), the 3-way interaction, and all 2-way interactions (independent variables). Results of habitat-type comparisons are not presented here (Warren 2001, Warren and Anderson 2005) and are only included to test the interaction of habitat with year and month. Additionally, data from the mowed portions of each field in 2000 were only used if results between mowed and unmowed portions were not significantly different (Warren 2001). We considered all tests to be significant at P < 0.05. Following a significant ANOVA, we used Tukey’s multiple comparison test to separate means. Results We identified 13 species of birds in 1999, 27 in 2000, and a total of 28 different species for both years (Table 2). The 3 most numerous species were Bobolink, Eastern Meadowlark, and Savannah Sparrow. Agelaius phoeniceus (Red-winged Table 2. Maximum number of birds counted during weekly bird surveys on 6 grasslands of the Canaan Valley National Wildlife Refuge, Tucker County, WV, May to August 1999–2000. Tracts: B = Beal, Ha = Harper, T = Thompson, C = Cortland, F = Freeland, and He = Hertz. Tract Common name Scientific name B Ha T C F He Bobolink Dolichonyx oryzivorus (L.) 4 8 70 3 145 0 Savannah Sparrow Passerculus sandwichensis (Gmelin) 11 2 6 3 4 8 Eastern Meadowlark Sturnella magna (L.) 21 2 3 0 5 0 Red-winged Blackbird Agelaius phoeniceus (L.) 2 7 11 1 5 3 Grasshopper Sparrow Ammodramus savannarum (Gmelin) 3 2 0 0 0 0 Vesper Sparrow Pooecetes gramineus (Gmelin) 0 0 0 0 0 1 Chipping Sparrow Spizella passerina ((Bechstein) 0 0 0 1 0 5 Field Sparrow Spizella pusilla (Wilson) 0 1 0 1 0 1 Eastern Towhee Piplio erythrophthalmus (L.) 0 0 0 0 0 1 Indigo Bunting Passerina cyanea (L.) 0 1 0 1 0 0 Song Sparrow Melospiza melodia (Wilson) 0 2 0 1 1 0 Canada Goose Branta canadensis (L.) 0 0 19 0 0 0 Mallard Anas platyrhynchos L. 0 0 1 0 0 0 Wild Turkey Meleagris gallopavo L. 7 0 0 0 0 0 Northern Harrier Circus cyaneus (L.) 1 0 0 0 0 0 Ruby-throated Hummingbird Archilochus colubris (L.) 0 0 0 1 0 0 Northern Flicker Colaptes auratus (L.) 2 0 2 1 0 2 American Crow Corvus brachyrhynchos Brehm 0 0 0 1 0 0 Carolina Wren Thryothorus ludovicianus (Latham) 0 0 0 1 0 2 Gray Catbird Dumetella carolinensis (L.) 0 0 0 2 0 0 Eastern Bluebird Sialia sialis (L.) 0 0 0 1 0 0 American Robin Turdus migratorius L. 1 0 0 0 0 0 Cedar Waxwing Bombycilla cedrorum Vieillot 0 2 0 0 0 0 Red-eyed Vireo Vireo olivaceus (L.) 0 0 0 1 0 0 Common Yellowthroat Geothlypis trichas (L.) 0 0 3 1 1 4 American Goldfinch Carduelis tristis (L.) 0 0 0 1 0 1 Northern Cardinal Cardinalis cardinalis (L.) 0 0 0 1 0 0 Turkey Vulture Cathartes aura (L.) 0 0 0 0 0 4 Southeastern Naturalist K.A. Chadbourne and J.T. Anderson 2015 Vol. 14, Special Issue 7 349 Blackbird) and Savannah Sparrows occurred most frequently and occupied all 6 fields. Bobolinks occurred on 5 of the 6 grasslands; we observed Eastern Meadowlark, Colaptes auratus (Northern Flicker), and Geothlypis trichas (Common Yellowthroat) on 4 fields; Spizella pusilla (Field Sparrow) and Melospiza melodia (Song Sparrow) on 3 fields; and Grasshopper Sparrow and Spizella passerina (Chipping Sparrow), Thryothorus ludovicianus (Carolina Wren), and Carduelis tristis (American Goldfinch) on two. We recorded the other 16 species on only one grassland (Table 2). Bird numbers showed different temporal trends during May and June of the 2 years, but varied in later months (Fig. 2). During 1999, populations rose through July and early August, then they declined (Fig. 2). In 2000, numbers peaked earlier, in mid-July, but at a lower level before declining drastically (Fig. 2). Observers frequently encountered many Bobolinks and Red-winged Blackbirds on the Freeland and Thompson tracts during July and August 1999. At the end of 1999’s breeding season, observers found large flocks of Eastern Meadowlarks on the Beall tract. Total density (number/acre [number/ha]) was greater in 1999 (mean = 3.34/ac, SE = 1.04 [8.25/ha, SE = 2.58]) than in 2000 (mean = 0.61/acre, SE = 0.13 [1.50/ha, SE = 0.32]) (F1, 32 = 11.53, P = 0.002). We also detected differences among months (F3, 32 = 3.83, P = 0.009), with a higher mean density in July than May, June, and August (Fig. 3). Densities were similar between years and among Figure 2. Total birds counted for weekly bird surveys on the Canaan Valley National Wildlife Refuge, Tucker County, WV, May–August in 1999–2000. Week 1 is the 2nd week in May, and Week 13 is the 2nd week in August. Southeastern Naturalist K.A. Chadbourne and J.T. Anderson 2015 Vol. 14, Special Issue 7 350 months for the Bobolink (years: F1, 32 = 0.06, P = 0.803; months: F3, 32 = 0.17, P = 0.915), Eastern Meadowlark (years: F1, 32 = 0.36, P = 0.551; months: F3, 32 = 0.69, P = 0.563), and Savannah Sparrow (years: F1, 32 = 0.52, P = 0.477; months: F3, 32 = 3.04, P = 0.068) (Table 3). Grassland bird diversity was similar between 1999 (mean = 0.12/acre, SE = 0.02 [0.29/ha, SE = 0.05]) and 2000 (mean = 0.16/acre, SE = 0.02 [0.39/ha, SE = 0.04]) (F1, 32 = 3.31, P = 0.078). However, species diversity was lower in August than other months (F3, 32 = 6.52, P = 0.001; Fig. 4). Grassland-bird richness was higher in 2000 (mean = 0.73, SE = 0.10 [1.81/ha, SE = 0.25]) than in 1999 (mean = 0.28, SE = 0.11 [0.69/ha, SE = 0.26]) (F1, 32 = 23.32, P < 0.0001). Figure 3. Breeding grassland bird density for all species combined among months on the Canaan Valley NWR, Tucker County, WV, May–August in 1999–2000. The same letter above bars indicates no difference (P > 0.05) among months. Figure 4. Breeding grassland bird diversity (Shannon- Weiner diversity indices; Zar 1999) among months on the Canaan Valley NWR, Tucker County, WV, May– August in 1999– 2000. The same letter above bars indicates no difference (P > 0.05) among months. Southeastern Naturalist K.A. Chadbourne and J.T. Anderson 2015 Vol. 14, Special Issue 7 351 Table 3. Breeding grassland bird density (number/ha), diversity, and richness by year and month on the Canaan Valley National Wildlife Refuge, Tucker County, West Virginia, May–August 1999 and 2000. 1999 2000 May June July August May June July August Species Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE Overall 2.13 0.49 5.44 1.13 14.64 7.07 10.8 7.27 1.65 0.56 1.65 0.56 2.52 0.98 0.95 0.45 Bobolink 0.31 0.21 0.3 0.23 2.45 1.91 5.18 3.57 0.27 0.21 0.71 0.56 1.45 1.15 0.25 0.16 Eastern Meadowlark 0.27 0.18 0.24 0.11 0.25 0.14 0.12 0.12 0.04 0.04 0.16 0.06 0.15 0.07 0.17 0.09 Savannah Sparrow 0.35 0.14 0.57 0.15 0.25 0.12 0.05 0.03 0.22 0.1 0.37 0.14 0.45 0.11 0.35 0.14 Diversity 0.35 0.09 0.42 0.11 0.35 0.06 0.03 0.02 0.48 0.06 0.47 0.07 0.52 0.06 0.22 0.06 Richness 0.72 0.12 0.98 0.23 1.02 0.3 0.23 0.1 1.09 0.14 1.11 0.19 1.32 0.16 0.54 0.09 Southeastern Naturalist K.A. Chadbourne and J.T. Anderson 2015 Vol. 14, Special Issue 7 352 August data showed a lower mean richness than May, June, and July (F3, 32 = 4.38, P = 0.011; Fig. 5). Discussion Overall, the diversity, richness, and often the abundance of the Valley’s grassland bird species were low compared to other states such as Iowa (Bryan and Best 1991); Kansas (Klute et al. 1997); and the Dakotas, Minnesota, and Montana (Johnson and Schwartz 1993). Avian diversity and richness were also low compared to other habitat types in West Virginia (Duguay et al. 2001, Forcey and Anderson 2002, Sacilotto 2002). However, abundance estimates were similar to those for grassland birds in Illinois (Kershner and Bollinger 1996). Our study was conducted in interior grassland habitats, which precluded some edge-dependent species from our surveys. Therefore, the Refuge grasslands’ low diversity is probably due to the state’s few grassland species rather than a problem with the Refuge’s habitat quality. The Valley’s grasslands provide important habitat for grassland birds in West Virginia (Warren and Anderson 2005). The three most abundant species—Savannah Sparrow, Bobolink, and Eastern Meadowlark—are primarily ground nesters that have limited numbers and distributions in the state due to a paucity of habitat. Indeed, the Bobolink is listed as a state rare species (WVDNR 2000), and the Eastern Meadowlark and Savannah Sparrow are declining at all scales (Sauer et al. 2012). Grassland habitat is relatively scarce in the state, and only hayfields and pastures, such as those evaluated in this study, or abandoned mine lands, provide suitable habitat for many grassland bird species (Forcey and Anderson 2002, Whitmore 1980, Whitmore and Hall 1978, Wray et al. 1982). Our study fields also provided edge and early-successional habitats, the latter a declining habitat type in the eastern US (Hunter et al. 2001). Figure 5. Breeding grassland bird richness by month on the Canaan Valley National Wildlife Refuge, Tucker County, WV, May–August in 1999–2000. The same letter above bars indicates no difference (P > 0.05) among months. Southeastern Naturalist K.A. Chadbourne and J.T. Anderson 2015 Vol. 14, Special Issue 7 353 The overall density and richness of birds living in the Refuge’s grasslands varied between the two years. Birds occurred at a greater mean density in 1999 mainly due to the many Bobolink flocks (>100 birds) and abundant Eastern Meadowlarks and Red-winged Blackbirds present. These differences may be partly attributed to inter-annual differences in weather. West Virginia experienced a drought in 1999 and normal precipitation in 2000 (NOAA 1999, 2000). In the Valley, the May–August total precipitation increased 8.6 inches (21.9 cm) between 1999 and 2000 (Fig. 1). Precipitation may have indirectly influenced grassland bird distributions and patterns in the Valley and surrounding areas during both years. Variations in grassland bird densities have been linked with drought even though this effect seems to be short-lived; most species recover within one year (Cody 1985, Dale 1984, George et al. 1992, O’Connor et al. 1999). Although drought may affect seasonal variations in grassland bird densities, it may ultimately be farmers’ responses to weather conditions that affect variations in the Valley’s bird densities. Most farmlands were mowed early in 1999 (June) because dry weather allowed farmers to access their fields. The mowing on non-Refuge land reduced available grassland habitat outside of the Refuge, causing birds to concentrate on the Refuge’s unmowed grasslands. In 2000, most farmers delayed mowing until mid- to late July because of abundant rain and wet fields, providing additional off-Refuge habitat for birds in 2000. While differences in average rainfall may have influenced the farmers’ responses, we suggest that it is unlikely that inter-annual weather differences directly altered the Refuge’s grassland bird populations. Differences between the Valley’s public and private lands may have also contributed to the variation in bird populations. Although increases in rainfall may not alter grassland bird density, diversity, or species richness directly, increased rainfall may affect nesting success and land management techniques. Flooding during prolonged periods of above-average rainfall can lead to nest loss of some grassland bird species (Wray et al. 1982), just as the lack of rain in 1999 probably reduced the number of species present on the fields. Thus, the results from 2000 probably indicate normal conditions. The diversity, richness, and density of grassland birds on The Refuge were lower in August than in other months because by then most of them had formed flocks or abandoned their territories. By August, the birds were using alternate sites that provided optimal foraging conditions for fledglings and for fueling their upcoming fall migration. Most species aggregated in different parts of the Valley or adjacent to transects. Bobolinks, among the first to migrate, began flocking in mid- to late July, prior to molting. Savannah Sparrows, which tend nests through August, were among the last species to leave. Management Implications The habitat provided in the Refuge for grassland birds in West Virginia is important because outside the Refuge this type of environment is limited to farmlands and reclaimed strip mines (Whitmore and Hall 1978). As small-scale farming Southeastern Naturalist K.A. Chadbourne and J.T. Anderson 2015 Vol. 14, Special Issue 7 354 became less feasible, fields were abandoned and succession changed the vegetation’s structural characteristics, greatly reducing grassland acreage (Whitmore and Hall 1978). Moreover, prior to widespread strip-mine reclamation, the Grasshopper and Vesper Sparrows were declining in their ranges (Whitmore and Hall 1978). Idle and active agricultural fields and reclaimed mine sites, if managed correctly, may provide essential habitats for these and other declining grassland species. With active management, the Refuge’s grasslands will provide crucial habitat for West Virginia’s grassland birds. Refuge staff must decide if they want to actively manage these fields as grassland habitats for state-listed rare species or allow them to revert to scrub-shrub and eventually to forest. Acknowledgments We thank the US Fish and Wildlife Service (Canaan Valley National Wildlife Refuge); West Virginia Division of Natural Resources (Wildlife Diversity Program); West Virginia University Division of Forestry and Natural Resources; the Davis College of Agriculture, Natural Resources, and Design at West Virginia University (Brown Faculty Development Fund); and the West Virginia Agricultural and Forestry Experiment Station (McIntire- Stennis) for providing funds. We also thank J.D. Osbourne and two anonymous referees for reviewing this manuscript. C.A. Rhoads and S.K. Reilly assisted with data collection. R.C. Whitmore and L. Butler reviewed an earlier version of this manuscript. This is manuscript number 3196 of the West Virginia University Agricultural and Forestry Experiment Station. Literature Cited Best, L.B., H. Campa, III, K.E. Kemp, R.J. Robel, M.R. Ryan, J.A. Savidge, H.P. Weeks, Jr., and S.R. Winterstein. 1997. 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