Avian use of early successional habitats: Are regenerating forests, utility right-of-ways and reclaimed surface mines the same?

Forest Ecology and Management 236 (2006) 76–84 www.elsevier.com/locate/foreco

Avian use of early successional habitats: Are regenerating forests, utility right-of-ways and reclaimed surface mines the same? Lesley P. Bulluck *, David A. Buehler Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN 37996, USA Received 5 July 2006; received in revised form 3 August 2006; accepted 22 August 2006

Abstract The importance of early successional habitats for breeding and post-breeding birds has received recent attention. Common early successional habitats in the eastern United States are regeneration after timber harvests, utility right-of ways and reclaimed surface mines. Few studies, however, have compared the characteristics of these with regard to avian habitat use. We conducted a passive mist-netting study to assess the breeding and post-breeding avian communities associated with these land uses in the Cumberland Mountains of eastern Tennessee. We used analysis of variance to compare the vegetation structure among these habitat types and discriminant function analyses to illustrate differences in vegetation structure and bird abundance among habitats. We banded 1562 individuals of 40 species (1.08 birds/net-hour). The percent cover of saplings, forbs and grass differed among habitat types, but there was no detectable difference in shrub cover. Vegetation structure allowed good discrimination between habitat types (Wilks’ l = 0.16), specifically in differentiating clearcuts from surface mines and right-of-ways. Although the three habitat types had several avian species in common, the abundance of 12 species differed substantially among habitat types, and their species abundance patterns allowed for excellent discrimination between these habitat types (Wilks’ l = 0.08). We conclude that these three early successional habitat types are different with regard to vegetation structure and avian community assemblage. These differences are important for local and landscape-scale conservation planning for both early and late successional avian species. # 2006 Elsevier B.V. All rights reserved. Keywords: Avian conservation; Avian community; Bird abundance; Regenerating clearcuts; Early successional habitats; Discriminant function analysis; Postbreeding season; Reclaimed coal surface mines; Utility right-of-way

1. Introduction Early successional habitats have received recent attention regarding their importance for breeding and non-breeding, migrant and resident bird species. By ‘‘early successional’’ we are referring to post-disturbance plant communities. Many populations of birds that breed in early successional areas are declining throughout the eastern United States because of loss of habitat (Askins, 2001; Brawn et al., 2001; Hunter et al., 2001; Dettmers, 2003). Furthermore, species that breed in interior mature forests may utilize early successional habitats during the post-breeding season (Marshall et al., 2003). This shift in habitat use has been attributed to the increased food availability and protective cover afforded by early successional areas; both of which are necessary for vulnerable fledglings and molting

* Corresponding author. Tel.: +1 865 974 8749; fax: +1 865 974 4714. E-mail address: [email protected] (L.P. Bulluck). 0378-1127/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2006.08.337

adults (Vega Rivera et al., 1999; Pagen et al., 2000; King et al., 1998, 2001). Despite the importance of these habitats and efforts to create specific types of early successional habitats for declining species such as Northern Bobwhite (Colinus virginiana) and Golden-winged Warbler (Vermivora chrysoptera), the diversity of different early successional habitat types has not been fully recognized in the literature. Most research to date regarding avian use of early successional habitats has documented species occurrence and/or reproduction in different types of timber harvests (Pagen et al., 2000; Marshall et al., 2003; Rodewald and Vitz, 2005; Vitz and Rodewald, 2006) or in utility right-of-ways (King and Byers, 2002; Confer and Pascoe, 2003) during the breeding and post-breeding seasons. Although timber regeneration areas may not ‘‘succeed’’ in a classical sense into another forest type for centuries, if at all, we refer to them as early successional for convenience and consistency with other publications dealing with habitat for birds. Likewise, utility right-of-ways are maintained in a state of arrested succession to

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prevent vegetation interference with transmission of electricity. Timber harvests, particularly clearcuts, have received the most attention in the avian literature relative to other early successional habitat types. This is not surprising considering the incidence of timber management on both public and private lands throughout the eastern United States. Maintaining a mosaic of different stand age classes (i.e., differing years postharvest) in a given landscape can provide habitat for a diversity of avifauna, especially when the requirements of regional species of concern, patch size and landscape context are considered (King et al., 1998, 2001; Krementz and Christie, 2000; Rodewald and Yahner, 2000, 2001; Gram et al., 2003; King and DeGraaf, 2004). The potential of utility right-of-ways to provide early successional habitat for wildlife has also been recognized. Several symposia on the environmental concerns in rights-ofway management have been held over the past 30 years (Goodrich-Mahoney et al., 2000), but only recently have specific studies on the use of utility right-of-ways by wildlife become common in the scientific literature (Gates, 1991; Chasko and Gates, 1992). Right-of-ways can be managed in a variety of ways, though they are usually sprayed with selective herbicides or treated mechanically to periodically reduce the height of woody vegetation. Recent studies have documented successful reproduction and high avian diversity in right-ofways, and have suggested the influence of right-of-way width and management type on avian diversity and nesting success (King and Byers, 2002; Confer and Pascoe, 2003). The use of reclaimed surface mines as avian habitat in North America has received less attention in the literature (Majer, 1989), with the majority of studies addressing birds in mineassociated wetlands (Horstman et al., 1998; Lacki et al., 2004) or mines in the midwestern US that have been reclaimed to expansive grasslands (Bajema and Lima, 2001; Bajema et al., 2001; Scott et al., 2002). Reclamation of mines to grasslands is also common in the Appalachians from Tennessee to Pennsylvania (Cox and Maehr, 2004) where mines are large (i.e., thousands of hectares) as a result of mountaintop removal mining. Research conducted in West Virginia by Wood et al. (2006) suggests that the mountaintop removal-valley fill mining technique that creates these large grasslands negatively affects Cerulean Warblers by removing the forested ridge habitats preferred by this species. However, many coal mines in Tennessee that were reclaimed more than 15 years ago were <100 ha in size. Many of these sites were planted with herbaceous and woody vegetation and are now mature shrub/ woodlands with a persistent herbaceous layer that are surrounded by mature forest. Hence, these sites may support a diverse avifauna comprised of both early and late successional species that differs in species composition and/or abundance compared with regenerating clearcuts and utility right-of-ways. The importance of successional shrublands to birds is apparent, however, few studies have simultaneously compared different types of early successional habitat that exist across most of the eastern US landscape (but see Fink et al., 2006). Furthermore, regional plans for wildlife habitat may too often assume that all early successional shrubland habitats are equal.

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State and federal agencies in the eastern United States are currently implementing timber harvests and low-intensity prescribed fire to create and maintain early successional habitat for songbirds and other disturbance-dependent wildlife. There is also recent interest in the restoration of the historically common open oak woodlands and savannas in the southern Appalachian region (Van Lear and Harlow, 2002; Van Lear, 2004). However, we do not fully understand whether the vegetation structure differs among these early successional habitats, and if so, how these differences affect avian abundance and/or composition. Our research compared the vegetation structure and avian communities within three types of early successional habitat during the late breeding season (late June and July). We chose this period of the breeding season because we wanted to account for the use of these habitats not only by species using them for breeding, but also by post-breeding, forest interior songbirds that often disperse into early successional habitats. Specifically, our first objective was to compare the vegetation structure in regenerating forests, utility right-of-ways and reclaimed coal surface mines to see if the percent cover of saplings, shrubs, forbs and grasses differed. Our second objective was to compare avian abundance and community structure in regenerating forests, utility right-of-ways and reclaimed coal surface mines. We tested the null hypothesis that there were no differences in vegetation and avian community structure across these three habitat types. 2. Methods 2.1. Study area We conducted this study in the Cumberland Mountains of northeastern Tennessee. These mountains comprise the southwestern portion of the Appalachian Mountains and extend into southeastern Kentucky. The mean elevation of the Cumberland Mountains is 580 m and the highest ridges are 1075 m. More than 50,500 ha of this landscape are publicly owned by the Tennessee Wildlife Resources Agency (TWRA), and our six study sites (two regenerating clearcuts, two utility right-ofways and two reclaimed surface mines) are located within the Royal Blue and Sundquist wildlife management areas (Campbell and Anderson counties). The predominant landcover of the region is mixed-mesophytic forest and approximately 8–10% is in early-mid succession because of the surface mining of coal, timber harvests and utility right-of-ways (Bulluck and Buehler, unpublished data). Despite the fact that the state owns large tracts of land as wildlife management areas, the state wildlife agencies do not have the mineral and timber rights on these very same tracts of land. Currently, an average of 800 ha of timber harvests and at least 200 ha of surface disturbance resulting from surface coal mining occurs annually in the study area. In Tennessee, reclaimed surface mines are typically the result of contour surface mining where coal is extracted from a seam that runs along an elevational contour. This practice creates fairly linear early successional areas that are typically 80–200 ha in size (although recent technology has allowed for

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much larger and wider contour mines). Occasionally, a coal seam lies close enough to the ridge top such that the entire ridge is removed and an early successional area encompasses the mountaintop. These mines can be up to 4000 ha in area, but are uncommon in Tennessee compared to other parts of the Appalachians. Timber harvesting is common in the region and occurs on both private and public lands. Individual harvests are typically clearcuts, or less commonly shelterwood cuts, and range in size from 10–30 ha. Approximately 56 linear km of utility right-of-way run through the region, are typically 20– 30 m wide, and are maintained by periodic application of selective herbicides approximately every 5 years. Prescribed fires are implemented by the state wildlife agency in both the fall and spring to maintain early successional areas (50–500 ha annually) and arson fires typically burn 100 ha annually (S. Stooksbury, TWRA, personal communication). 2.2. Field methods We used passive mist-netting to capture birds in two regenerating clearcuts, two reclaimed coal surface mines and two utility right-of-ways for 3 days each (n = 18 days) in 2004 and for 2 days each (n = 12 days) in 2005. We selected these six study sites opportunistically to ensure similar successional stages within a habitat type, similar elevation among all sites (between 600 and 950 m) and moderate accessibility in the region’s rugged terrain. This range of elevation did not appear to be biologically significant because the vegetation species composition was very similar within and across habitat types (i.e., there was not a shift in ecosystem or forest type as might be expected above this elevation in the Appalachian Mountains). The two clearcuts were 5–6 years post-harvest and were surrounded by mature forest. Woody regeneration was predominantly oaks (Quercus spp.), maples (Acer spp.), yellow poplar (Lireodendron tulipifera), sourwood (Oxydendrum arboreum) and sassafras (Sassafras albidum) with abundant blackberry (Rubus spp.) throughout. The two surface mines were reclaimed 15–20 years before the study with an herbaceous layer of grasses and forbs and black locust (Robinia pseudoacacia) saplings. Since reclamation, maples, yellow poplar and oak have become established as well as thickets of blackberry. These two mines were also burned by arson within the last 5 years and therefore snags were common. The two right-of-ways were maintained with selective herbicides and have a similar assemblage of saplings and shrubs as the clearcuts and older surface mines. All mist-netting took place between 20 June and 20 July in both years. We chose to sample at this time to capture both birds that bred on site, as well as individuals that that nest in the surrounding mature forests and disperse into these early successional areas once their young have fledged. We opened 10 nets at each site (two 6 m, four 9 m and four 12 m) from sunrise (06:00 h) to noon (12:00 h) on days when it was not raining or too windy to assure equal capture potential. To calculate net-hours, we treated one standard, 12 m net operated for 1 h as one net-hour (Ralph et al., 1993) such that we banded for 48 net-hours per day and 480 net-hours total per site. We

banded each bird with a United States Fish and Wildlife Service metal band (permit #22585) and recorded the species, sex (male, female or unknown), age (hatch-year or after hatchyear), weight, wing and tail length, fat score and molt status according to Pyle (1997). We also noted whether after hatchyear birds displayed evidence of recent or current breeding (i.e., brood patch for females or cloacal protuberances for males). We released birds in <20 min from the same site where they were captured. If we captured an individual twice in 1 day, we only used the initial capture data. Because of the linear nature of the right-of-way and mine sites, we were unable to avoid forest edges in our sampling. We could have placed nets in clearcuts farther from forest edges because these sites had a smaller edge to interior ratio, but we chose to place all mist nets between 10 and 40 m from a forest edge across all three habitat types so that the mean distance to forest edge did not differ across treatments. We collected vegetation data at each site by visually estimating the percent cover of saplings, shrubs, forbs and grasses within 5 m around each mist net. The percent cover of these vegetation types could sum to >100% such that there was no dependence among cover types. 2.3. Statistical analyses We pooled bird data across the 2 years because we were more interested in the differences among habitat types than in annual variation. To evaluate the similarity in the species composition among the habitat types, we computed the Jaccard index (Gotelli and Ellison, 2004, p. 404) for each pairing of the three habitats. We used analysis of variance (ANOVA) to compare the mean percent cover of saplings, shrubs, forbs and grasses in the three treatments and Tukey’s honestly significant difference (HSD) to carry out multiple comparisons tests using JMP Statistical Software v. 5.1.2 (2004). We used discriminant function analysis (DFA) to illustrate differences in vegetation structure and avian abundance across habitats using NCSS statistical software (Hintze, 2001). In the vegetation DFA, we used mean percent cover of saplings, shrubs, forbs and grass as the independent variables and habitat type as the grouping variable. In the species DFA, we used species abundance (mean number of captures/net-hour) for the 28 most abundant species (i.e., those captured more than 10 times) as the independent variables and habitat type as the grouping variable. In both DFAs, mist net was considered the sampling unit (n = 20 nets/habitat type). The large number of species used in the species DFA has the tendency to inflate the between-group variation and cause a problem of model overspecification (Manly, 1994; Brawn, 2006). However, our analysis was mainly for exploratory purposes and the primary objective of the DFA was to identify the species that were most influential in differentiating between the three habitat types. 3. Results The percent cover of saplings (F = 14.35, P < 0.0001), forbs (F = 16.96, P < 0.0001) and grass (F = 10.61,

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Table 1 Summary of capture rates, number of species captured and Shannon Wiener diversity (H0 ) for clearcuts, right-of-ways and reclaimed surface mines during late June and July of 2004 and 2005 in the Cumberland Mountains, Tennessee Treatment Clearcut Utility ROW Surface mine Total

Number of captures

Net-hoursa

Number of birds/net-hour

Number of species

H0

372 572 618

480 480 480

0.78 1.19 1.29

30 33 34

4.16 4.34 4.42

1545

1440

1.08

40

4.48

a

One net-hour is equal to one standard, 12 m  2.5 m net being operated for 1 h. Fig. 1. Mean percent cover of saplings, shrubs, forbs and grass for regenerating clearcuts (CC), utility right-of-ways (ROW) and reclaimed coal surface mines. Bars with the same letters indicate no significant difference with the multiple comparisons Tukey HSD test (P < 0.05).

P < 0.0001) differed among early successional habitat types, but there was no detectable difference in the percent cover of shrubs (F = 1.17, P = 0.33) (Fig. 1). Specifically, the percent cover of saplings was greater in regenerating clearcuts than in right-of-ways and surface mines. On the other hand, the percent cover of forbs was greater in right-of-ways and surface mines compared with regenerating clearcuts. Lastly, the percent cover of grass was greatest in surface mines, intermediate in right-ofways and least in regenerating clearcuts (Fig. 1). Vegetation structure allowed for good discrimination among the different habitat types (Wilks’ l = 0.17) (Fig. 2), with 83% of the sample variation in vegetation structure accounted for by habitat type. We captured 1562 individuals of 40 different species (1.08 birds/net-hour) across all 6 sites and 2 years (Table 2). We

captured 30 species in regenerating clearcuts, 33 in utility rightof-ways and 34 in reclaimed surface mines. Shannon Wiener diversity was greatest for reclaimed surface mines (4.42), intermediate for right-of-ways (4.34) and lowest for clearcuts (4.16). The Jaccard index of similarity was 0.72 for clearcuts and surface mines, 0.73 for clearcuts and right-of-ways and 0.83 for surface mines and right-of-ways. Clearcuts had a lower capture rate (0.78 birds/net-hour) than right-of-ways and surface mines (1.19 and 1.29 birds/net-hour, respectively) (Table 1). Sixty percent of the species (n = 24) and 43% of the individuals were mature forest-breeding species; the remainders were scrub-breeding species (Ehrlich et al., 1988). Eightynine percent of the after hatch-year captures showed signs of current or recent breeding condition (i.e., females had evidence of a brood patch or males had a cloacal protuberance). A larger proportion (91%) of the after hatch-year scrub-breeding birds showed evidence of recent or current breeding condition compared with after hatch-year mature forest-breeding birds (86%). Hatch-year birds comprised 45% of all captures; 58% of

Fig. 2. Canonical-variate plot from a discriminant function analysis of vegetation structure (mean percent cover of saplings, shrubs, forbs and grass) in the three different successional habitat types. Sapling cover is greater for smaller values on the canonical score 1 axis while forb and grass cover are greater for larger values on the canonical score 1 axis. The dotted lines represent 90% confidence ellipses.

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the mature forest-breeding captures were hatch-year birds while only 34% of the scrub-breeding captures were hatch-year birds. The proportion of mature forest- to scrub-breeding birds did not differ across habitat types. Bird communities were similar across habitat type with many species occurring equally in all three habitats (e.g., Carolina Wren, Field Sparrow, Hooded Warbler, Northern Cardinal and Red-eyed Vireo). Some species (n = 8) were only found in one of the three habitats; six of these were only captured on one or two occasions (Table 2), and Prairie Warblers and Brown Thrashers occurred only in clearcuts and utility right-of-ways, respectively. Many other species were captured in more than one habitat type, yet were most abundant in one of the habitat types. For this reason, species abundance allowed for excellent discrimination (Wilks’ l = 0.08) such that 92% of the sample variation in species abundance was accounted for by habitat type (Fig. 3). Twelve of the 28 species had a significant influence on the discrimination between

habitat types (i.e., significant F-values in the DFA). Specifically, American Redstarts, Indigo Buntings and Kentucky Warblers were captured more frequently in utility right-of-ways and reclaimed surface mines than in regenerating clearcuts. Chestnut-sided Warblers, Eastern Towhees and Song Sparrows were highly associated with right-of-ways, whereas Black-and-white Warblers, Blue-headed Vireos, Cerulean Warblers, Common Yellowthroats and Goldenwinged Warblers were highly associated with reclaimed surface mines. 4. Discussion Our data demonstrated differences in vegetation structure, avian abundance and avian community structure in regenerating clearcuts, utility right-of-ways and reclaimed surface mines in the Cumberland Mountains of Tennessee. The differences in vegetation structure are somewhat intuitive because clearcuts

Table 2 Total number of individuals (n) captured across all sites and the capture rates (number of birds per 100 net-hours) for all species in the three measured habitat types Species

n

Clearcut

Reclaimed mine

Right-of-way

American Goldfinch (Carduelis tristis) American Redstarta (Setophaga ruticilla) Black-and-white Warblera (Mniotilta varia) Blue-grey gnatcatcher (Poliotila carulea) Blue-headed Vireoa (Vireo solitarius) Blackburnian Warbler (Dendroica fusca) Brown Thrasher (Toxostoma rufum) Black-throated-green Warbler (Dendroica virens) Carolina Chickadee (Poecile carolinensis) Carolina Wren (Thryothorus ludovicianus) Canada Warbler (Wilsonia candensis) Cedar Waxwing (Bombycilla cedrorum) Cerulean Warblera (Dendroica cerulea) Common Yellowthroata (Geothlypis trichas) Chestnut-sided Warblera (Dendroica pensylvanica) Downy Woodpecker (Picoides pubescens) Eastern Bluebird (Sialia sialis) Eastern Phoebe (Sayornis phoebe) Eastern Towheea (Pipilo erythrophthalmus) Eastern Wood-pewee (Contopus virens) Tufted Titmouse (Baeolophus bicolor) Field Sparrow (Spizella pusilla) Golden-winged Warblera (Vermivora chrysoptera) Hooded Warbler (Wilsonia citrina) Indigo Buntinga (Passerina cyanea) Kentucky Warblera (Oporornis formosus) Northern Cardinal (Cardinalis cardinalis) Ovenbird (Seiuris aurocapillus) Prairie Warblera (Dendroica discolor) Rose-breasted Grosbeak (Pheucticus ludovicianus) Red-eyed Vireo (Vireo olivaceus) Scarlet Tanager (Piranga olivacea) Song Sparrowa (Melospiza melodia) White-breasted Nuthatch (Sitta carolinensis) White-eyed Vireo (Vireo griseus) Worm-eating Warbler (Helmitheros vermivora) Wood Thrush (Hylocichla mustelina) Yellow-breasted Chat (Icteria virens) Yellow-throated Vireo (Vireo flavifrons)

61 79 53 2 15 3 5 31 18 79 2 7 13 38 85 7 1 40 51 1 13 136 18 180 183 39 37 72 15 10 45 11 20 1 27 45 5 113 1

1.67 1.88 2.08 0.42 0.00 0.00 0.00 1.25 1.67 5.63 0.00 1.25 0.21 0.21 0.63 0.42 0.00 0.83 2.29 0.21 2.08 6.25 0.00 12.08 7.50 0.83 2.92 3.13 3.13 0.00 3.33 0.42 0.21 0.00 2.08 2.29 0.21 10.42 0.00

5.42 5.83 6.04 0.00 2.29 0.21 0.00 3.54 1.25 6.04 0.00 0.00 1.88 5.21 6.25 0.63 0.00 4.38 2.29 0.00 0.21 8.75 3.33 13.33 16.04 4.38 2.08 7.29 0.00 1.04 3.33 1.46 0.83 0.21 1.25 4.38 0.21 7.29 0.21

5.63 8.75 2.92 0.00 0.83 0.42 1.04 1.67 0.83 4.79 0.42 0.21 0.63 2.50 10.83 0.42 0.21 3.13 6.04 0.00 0.42 13.33 0.42 12.08 14.58 2.92 2.71 4.58 0.00 1.04 2.71 0.42 3.13 0.00 2.29 2.71 0.42 5.83 0.00

Species caught fewer than 10 total times were not use in analyses. a Species that contributed significantly to the discrimination between habitats based on their abundances across the habitat types.

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Fig. 3. Canonical-variate plot from a discriminant function analysis of species abundance (mean number of captures/net-hour) in three different successional habitat types. The dotted lines represent 90% confidence ellipses. The four-letter species codes are provided for the species whose abundances contributed significantly to the discrimination between habitats: Golden-winged Warbler (GWWA), Blue-headed Vireo (BHVI), Cerulean Warbler (CERW), Common Yellowthroat (COYE), Blackand-white Warbler (BAWW), Kentucky Warbler (KEWA), Indigo Bunting (INBU), American Redstart (AMRE), Chestnut-sided Warbler (CSWA), Song Sparrow (SOSP), Eastern Towhee (EATO) and Prairie Warbler (PRAW).

have a flush of sapling and blackberry regeneration that typically out-competes herbaceous cover, except for areas such as log landings and roads that are often seeded with grasses and forbs after harvest is complete. Therefore, clearcuts are comprised predominantly of dense saplings, with occasional patches of herbaceous cover. On the other hand, mines with poor, compacted soils are reclaimed with abundant herbaceous cover to prevent soil erosion. This herbaceous layer persists for many years, even as patchy woody vegetation becomes established. Utility right-of-ways managed with herbicides are somewhat intermediate between the two with dense saplings and shrubs as well as open areas with herbaceous cover. We do not think that the prevalence of snags in reclaimed mines (resulting from previous arson fires) affected our results. Although snags provide song perches during the breeding season and presumably aid males in guarding territory boundaries, the value of snags to songbirds during the postfledging period of the breeding season was probably not significant. The greater avian abundance and species richness found in right-of-ways and reclaimed surface mines compared with clearcuts may indicate the importance of herbaceous vegetation to ground-nesting and scrub-breeding species as well as the many forest-interior birds that utilize the diverse vegetation structure during the vulnerable post-breeding season. These results are similar to the findings of Confer and Pascoe (2003) who demonstrated that utility right-of-ways treated with herbicide and fire had more vegetation structure and greater densities of birds than those treated mechanically. Mechanical treatment of ROW vegetation creates conditions similar to a clearcut with a dense layer of saplings and shrubs with little herbaceous cover.

We also demonstrated differences in avian community structure across the three habitat types. While many species (n = 15, 37.5%) were found in similar abundances across all three habitat types (Table 2), there were distinct differences in abundance for several species (n = 12, 30%), resulting in good discrimination between the three habitat types based on avian abundance alone. Species abundance patterns were most effective in discriminating clearcuts from right-of-ways and surface mines, but discrimination between surface mines and right-of-ways was still apparent (Fig. 3). Fink et al. (2006) also found differences in avian abundance across three early successional habitat types in the Missouri Ozarks. Specifically, they found that habitat type (regenerating forests, glades and forest edges) was an important factor in explaining breeding density for five species. Our study provides a snapshot in time of three very dynamic systems. Early successional habitats are ephemeral, particularly regenerating forests after timber harvests and change through time in the absence of recurrent disturbance. On the other hand, the poor soils in reclaimed mines and the use of herbicides in rights-of-ways, maintain these areas as early successional habitat for longer periods of time than do clearcuts. Our results may have shown more or less discrimination among habitats had we sampled regenerating forests at different time periods postharvest rather than 5–6 years, or if we had included other types of naturally occurring early successional areas such as wetlands and high elevation balds. Our study provides a comparison of three prevalent and man-made early successional areas in the southeastern U.S. although care must be taken when extrapolating our results to other regions. For example, regenerating aspen stands in the upper midwest have a persistent and extensive herbaceous layer that may be more similar to reclaimed mines

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and right-of-ways than the regenerating mixed mesophytic forests in our study. Furthermore, reclaimed mines in other regions or even more recent mines in the Cumberland Mountains do not support the same avian species assemblage due to differences in patch size, landscape context, and vegetation used in reclamation (i.e., the lack of woody vegetation). If this research had been conducted in recently reclaimed mine sites within the same region, we suspect the results would be very different. For example, the species abundance and richness of birds would be very low since very few avian species use the grass monoculture that results from current reclamation practices. Mature forest-breeding birds made up a large proportion of our individual captures (43%) and species (58%) across all sites despite the fact that we were banding in early successional habitats. Because 58% of the mature forest-breeding individuals captured were hatch-year birds (compared with only 34% for scrub-breeding birds), we suspect that some of these individuals may have dispersed from nearby mature forestbreeding sites. This is consistent with research conducted in the predominantly forested landscapes of West Virginia (Marshall et al., 2003) and Ohio (Vitz and Rodewald, 2006) where species that breed in mature forests were found to be abundant in regenerating clearcuts during the post-breeding season. However, while conducting another research project on the reclaimed surface mines earlier during the breeding season (early May–mid June) we observed several woodland-breeding species using these sites. For example, Black-and-white Warbler, Blackburnian Warbler, American Redstart and Blue-headed Vireo nests were found on the reclaimed mine sites while Cerulean Warblers, Black-throated-green Warblers and Kentucky Warblers were observed nesting on the edges of these sites and foraging within them. Indeed, despite the need for a landscape with extensive mature forest cover, many of the mature forest species captured in this study were associated with areas of small-scale disturbance. The presence of mature forest-breeding birds in our sites may be due to the linear nature of surface mines and utility ROW and the subsequent decision to place nets between 10 and 40 m of forest edges. However, our results are consistent with several previous studies that suggest mature forest species occupy early successional areas during the post-fledgling period. For example, Hooded Warblers were found to be more abundant in hurricane caused forest gaps in southern Appalachian forests (Greenberg et al., 2001) and in areas with 60% hemlock (Tsuga canadensis) mortality in the northeastern United States forests (Tingley et al., 2002) compared with undisturbed areas. Likewise, Hunt (1998) found that early successional habitats in Vermont and New Hampshire forests may function as reproductive sources for the American Redstart when compared with mature forests. The evidence presented here and found previously suggests that early successional areas of small to moderate size located in a heavily forested landscape are certainly used by many late successional species. The species composition differed among the three types of habitats considered in this study, yet the ratio of mature-forest to shrub-breeding birds captured was similar across the three habitat types.

5. Conclusion Our goal was not to determine which early successional habitat type was better for avian conservation, rather, it was to determine whether these habitat types could be considered equivalent in terms of their vegetation and avian community structure. Our results suggest these habitats are not equal in the Cumberland Mountains of Tennessee with regard to the vegetation structure, avian abundance and avian species composition. There are important management and conservation implications of these findings, particularly at the landscape scale. Recommendations for maintaining historic amounts of early successional areas in the northeastern United States landscape, for example, are <6% (Litvaitis, 2003). The range of natural variability for early successional habitats has not been documented for the Cumberland Mountains in Tennessee, although approximately 10% of the area is currently classed as early successional habitat (Bulluck and Buehler, unpublished data), and there is a desire to maintain or increase this level by the state wildlife agency. If maintenance of such percentage goals of early successional habitat is met through a single type of management, the needs of all species may not be met. Reclaimed surface mines were unique in having the greatest abundances of mature forest associates, such as Black-andwhite Warbler, Blue-headed Vireo and Cerulean Warbler, while also having the greatest abundances of shrubland-breeding species such as Golden-winged Warbler and Common Yellowthroat. The mine sites sampled in this study are potentially reminiscent of the open woodlands found historically in this region (Brewster, 1886). These woodlands were previously maintained through frequent, low-intensity burns and xeric soils that promoted open understory forests with persistent herbaceous cover (Van Lear and Waldrop, 1989; Van Lear and Harlow, 2002). Most mine sites in the Cumberland Mountains that were reclaimed 20 years ago are characterized by poor, compacted soils and have been burned periodically by prescribed and arson fire, such that they contain both mature and young trees with persistent herbaceous cover. We do not advocate the surface mining of coal to create open woodlands; especially considering that modern extraction practices often create large, persistent grasslands of non-native species and the importance of maintaining extensive mature forest for declining species such as the Cerulean Warbler. We do want to demonstrate how the more mature reclaimed mine sites and utility right-of-ways that already exist in 8% of the predominantly forested Cumberland Mountain landscape are occupied by a diverse community of both late and early successional birds that is unique from that found in regenerating clearcuts. These sites can be maintained with prescribed fire without compromising the surrounding mature forest. No study to date has illustrated such differences between early successional habitat types that will likely be important for effective local and regional land-use planning for wildlife. Harvesting timber can be an efficient and effective means for wildlife management; however, it should not be considered the only way to create early successional habitat. Just as one age class of regenerating forest does not provide habitat for all

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