Abundance of Grassland Sparrows on Reclaimed Surface Mines in Western Pennsylvania1

Abundance of Grassland Sparrows on Reclaimed Surface Mines in Western Pennsylvania1 Jennifer A. Mattice,2 Daniel W. Brauning,3 and Duane R. Diefenbach4 ________________________________________ Abstract Introduction Grassland songbird populations have experienced some of Many North American grassland bird species have the most severe declines of any migratory songbird guild experienced severe and consistent population declines in North America and are continuing to disappear from during the past 30 years (Robbins et al. 1986, Herkert portions of their historic ranges. Habitat loss and degrada- 1994, Sauer et al. 1996). In fact, since 1966 the guild of tion have been implicated as primary causes of these de- grassland bird species had the lowest percentage of clines. However, intensive surface coal mining and subse- increasing species in the U.S. Breeding Bird Survey quent reclamation in western Pennsylvania have created (Pardieck and Sauer 2000). Population declines are large tracts of grassland habitat during the past 30 to 40 rooted in the near collapse of the native tallgrass prairie years. We estimated the area of habitat suitable for breed- ecosystem and severe losses in most other native prai- ing grassland songbirds on reclaimed strip mines in nine rie systems (Samson and Knopf 1994, Warner 1994). western counties of Pennsylvania using a stratified ran- Most states have lost 99 percent of their native tallgrass dom sample design. We used distance sampling methods prairie, and grasslands top the list of critically endan- to estimate abundance of Henslow’s (Ammodramus gered native ecosystems (Noss et al. 1995). henslowii), Savannah (Passerculus sandwichensis), and Grasshopper (Ammodramus savannarum) Sparrows. We Losses in native grassland ecosystems were largely the estimated that 35,373 ha (95 percent CI = 26,758 - result of conversion to agriculture. Many grassland bird 46,870) of reclaimed-mine grassland suitable for breeding species, however, adapted to newly created agricultural grassland songbirds were present in our 1.85 x 106 ha habitats, and those that exploited these habitats study area in 2001. Henslow’s, Savannah, and Grass- expanded their ranges eastward with the felling of th hopper Sparrow abundances were 4,884 (95 percent CI = Eastern forests during the 19 Century (Askins 1999). 2,128 – 8,460), 1,921 (95 percent CI = 848 – 2,790), and However, changes in agricultural practices during the 9,650 (95 percent CI = 4,390 – 13,614) singing males, past 50 years, including conversion of pastures and respectively. Reclaimed-mine grasslands in western hayfields to row crops, made much agricultural habitat Pennsylvania supported substantial grassland songbird unsuitable for native grassland species (Warner 1994). populations during the 2002 breeding season. Therefore, Population declines in grassland bird species observed management of reclaimed surface mine areas as grassland today reflect those changing practices and the loss of reserves may help prevent populations of some species, agricultural areas to urban sprawl (Vickery et al. 1999). notably Henslow's Sparrow, from becoming endangered. Widespread habitat loss, fragmentation, and consequent population declines have drawn considerable conservation and research attention to grassland bird communities. Key words: Ammodramus henslowii, Ammodramus Grassland symposia (Vickery and Herkert 1999) and savannarum, Grasshopper Sparrow, grassland birds, special sessions on grassland birds during national grassland habitat, Henslow's Sparrow, Passerculus meetings (this volume) have highlighted the plight of sandwichensis, Pennsylvania, reclaimed surface mine, these species and the need to understand their population Savannah Sparrow. dynamics and habitat needs. This is especially apparent for the Henslow’s Sparrow (Ammodramus henslowii), __________ previously evaluated as a candidate for the U.S. Endan- 1 gered Species List, which has a restricted geographic A version of this paper was presented at the Third Interna- range and low relative abundance (Smith 1992, Pruitt tional Partners in Flight Conference, March 20-24, 2002, Asilomar Conference Grounds, California. 1996). Although not recommended for Federal listing 2New Jersey Audubon Society, 11 Hardscrabble Road, (Federal Register 1998, 63(174) pp. 48162-64), it was Bernardsville, NJ, 07924. E-mail: [email protected] identified as one of the highest priority bird species on the 3 Pennsylvania Game Commission, 2001 Emerton Ave., National Audubon Society’s Watch List (Pashley 1996). Harrisburg, PA, 17110. Grasshopper Sparrows (Ammodramus savannarum) and 4U.S. Geological Survey, Pennsylvania Cooperative Fish and Wildlife Research Unit, Pennsylvania State University, 113 Savannah Sparrows (Passerculus sandwichensis) cur- Merkle Laboratory, University Park, PA 16802. rently have much wider geographic ranges but also have USDA Forest Service Gen. Tech. Rep. PSW-GTR-191. 2005 504 Grassland Sparrows in Pennsylvania – Mattice et al. experienced consistent population declines (Peterjohn and cally defensible population estimates for several grass- Sauer 1999). land bird species and an estimate of the area of suitable reclaimed surface mine habitat in western Pennsyl- With loss and degradation of native grassland habitats vania. Specifically, we attempted to quantify the con- and recognition that most agricultural habitat essen- tribution of reclaimed surface mines in western tially serves as a population sink (Bollinger et al. 1990, Pennsylvania to populations of three obligate grassland Kershner and Bollinger 1996, Rohrbaugh et al. 1999), bird species: Henslow’s Sparrows, Grasshopper Spar- managed habitat areas have become vital for many rows, and Savannah Sparrows. grassland bird communities. Agricultural set-asides (e.g., CRP lands) and prairie reserves provide reser- voirs of grassland habitat that may help support remaining populations of some grassland bird species Study Area (Delisle and Savidge 1997, Koford 1999, Coppedge et We conducted our study in nine western Pennsylvania al. 2001, Johnson and Igl 2001). In addition, reclaimed counties (Armstrong, Butler, Cambria, Clarion, Clear- surface mines have inadvertently become a source of field, Indiana, Jefferson, Somerset, and Venango), grassland bird habitat. Whitmore and Hall (1978) docu- totaling 18,648 km2, an area roughly equivalent to the mented the presence of grassland birds on reclaimed state of New Jersey (fig. 1). These counties overlay the surface mines 25 years ago, although the contribution main bituminous coal field in Pennsylvania (Cuff et al. of those populations was not recognized for many 1989), and coal is removed primarily by surface min- years. Recent studies have confirmed the existence of ing. Less than 30 percent of available coal has been substantial grassland bird populations on reclaimed mined in the majority of these counties. Post-mining mines throughout the Midwest and Northeast, which reclamation, conducted primarily since the 1960s, has indicates these habitats may be important for conser- restored topographical contours and established veget- ving many grassland species (Yahner and Rohrbaugh ative cover on disturbed soils using a grass mixture 1996, Bajema et al. 2001). dominated by fescue (Fescue spp.), clover (Trifolium spp.), and bird’s-foot trefoil (Lotus corniculatus) In the eastern United States, and particularly in Penn- (Buckwalter 1983, Piehler 1987, D. W. Brauning, pers. sylvania, reclaimed bituminous coal fields are bene- obs.). Trees and shrubs, primarily pine (Pinus spp.), ficial to grassland birds (Yahner and Rohrbaugh 1996). locust (Robinia spp.), and autumn olive (Elaeagnus Widespread surface mining and subsequent reclama- umbellata) were usually planted in reclaimed sites but tion in western Pennsylvania have resulted in an often failed to become established. extensive patchwork of reclaimed sites among forests, woodlots, and agricultural fields. The acidic, nutrient- poor soils of reclaimed sites provide little potential for agricultural or timber production, and grasses and Methods legumes tend to be the most successful and persistent vegetation types (Vogel 1981, J. Mattice pers. obs.). Quantification of Reclaimed Areas These often undisturbed fields have a slow rate of eco- We used a geographic information system (GIS) to logical plant succession, and they are ideal for overlay a square grid of 9-km2 blocks over the entire 9- Henslow’s Sparrows and compatible for many other county study area. For the purpose of creating a strat- grassland-associated species (Bajema et al. 2001). ified sampling scheme, we then used a GIS map of During a survey of the distribution of breeding birds in permitted and abandoned mine sites, combined with a Pennsylvania (Brauning 1992) conducted in the 1980s, vegetation cover classification map from the Penn- a large number of locations of grassland birds, in- sylvania Gap Analysis Project (PA GAP, Final Report, cluding Henslow’s, Grasshopper, and Savannah Spar- Pennsylvania State University and U.S. Geological rows, were on reclaimed surface mines. However, this Survey, June 2000), to estimate the percent area of survey did not provide abundance estimates, and pop- reclaimed surface mine in each block. However, an ulation sizes could not be quantified. In an attempt to informal evaluation of this GIS map found that document population trends for the Henslow’s Sparrow although it provided an indication of the amount and over its historic and current range, a federal status location

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