Feb 26, 1997 - Edited by: James R. (Randy) Williams. John W. Goodrich-Mahoney. Jan R. Wisniewski. Joe Wisniewski. Sponsored by: Entergy Services, Inc.
The Sixth International Symposium on Environmental Concerns in Rights-of-Way Management 24-26 February 1997 New Orleans, Louisiana, USA
Edited by: James R. (Randy) Williams John W. Goodrich-Mahoney Jan R. Wisniewski Joe Wisniewski
Sponsored by: Entergy Services, Inc. Electric Power Research Institute
with support from: American Cyanamid Company Edison Electric Institute Gas Research Institute New York Power Pool
Conference Co-Chairmen: James R. (Randy) Williams John W. Goodrich-Mahoney
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First Edition 1997 Library of Congress Cataloging ill Publication Data International Symposium on Environmental Concerns in Rights-of-Way Management (6th: 1997 : New Orleans, La.)
The sixth International Symposium on Environmental Concerns in Rights-of-Way Management: 24-26 February 1997, New Orleans. Louisiana / edited by James R. (Randy) Williams.n Yet al."; sponsored by Entergy Services, Inc. Yand" Electric Power Research Institute; conference cowchainnen: James R. (Randy) Williams, John W. GoodrichwMahoney. p. em. Includes index. ISBN 0-08-043 198-4 (he) 1. Public utilities~~Right ofWayw-Management--Congresses. 2. Environmental protcctiollw-Congrcsscs. I. Williams, James R. (James Randy) II. Entergy Services. m. Electric Power Research Institute. HD242.9.1581997 333.7 ..dc21 97-15931 CIP
Bl'itish Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library.
ISBN 008 0431984
Printed and bound ill Great Britain by Redwood Books
133
Optimal Management Strategies tor Biodiversity Within a Powerline Right-at-Way Matthew C. Perry, Peter C. Osenton, Frederick W. Fallon, and Jane E. Fallon
Management techniques used to control vegetation along a new 8.5 km {5.3 mile)-long powerline right-at-way located at Patuxent Research Refuge are being evaluated to identify changes in habitat that affect wildlife. Techniques include: complete mow, strip mow, low volume -foliar spray, selective basal spray, and tree topping. One hundred and one bird species were recorded during line transect sampling along the right-af-way. Fifteen species were recorded in numbers greater than ten individuals per visit in at least One season of the year. Nine species of mammals were trapped in live. traps during the study and four other mammal species were observed but not captured. Twelve species of amphibians and six species of reptiles were trapped in pitfall or funnel traps. Differences in the distribution of species seemed to be related to the physical and hydrological features of the right~of-way. Although no major differences in the distribution of wildlife species resulted from the vegetation management, differences are expected in the future as vegetation differences become more pronounced. Data from this study will be of value to resource managers attempting to provide optimal habitat for biodiversity.
Keywords:
Right~of-way,
powerline, biodiversity, wildlife, birds, mammals, amphibians, reptiles, traps
BACKGROUND AND JUSTIFICATION
A 500 kilovolt (kV) overhead transmission line was' constructed by the Baltimore Gas' and Electric Company (BGE) during 1994-95 as a portion of the last section of a 500 kV loop around Washington, D.C. One segment of this line goes through the North Tract of the Patuxent Research Refuge (Patuxent) adjacent to an existing 230 kV transmission line constructed in 1972. Patuxent is a 5120 ha (12,800 acre) research facility within the U.s. Deparhnent of the Interior and located in Laurel, Maryland. Within the North Tract, the right-ofway for both lines is approximately 8.5 km (5.3 miles) long, 92 m (300 ft) wide; and covers 77ha (193 acres). BGE has a regional responsibility to maintain a reliable transmission system utilizing cost-effective and environmentally compatible vegetation management techniques. These techniques traditionally include mowing, cutting with chain saws, and herbicide spraying of vegetation. A management plan has been developed by BGE in cooperation with Patuxent to provide optimal utiliza-
tion of the right-of-way by wildlife. Site-by-site prescriptions were outlined to guide construction activity and to prOVide a baseline for future maintenance practices. Several of the practices referenced in the Management Plan are experimental and in some instances must remain flexible during the maintenance process to meet the changing needs of both parties. The longterm commihnent by BGE to manage this diverse area provides an excellent opportunity to implement a concurrent research project to evaluate the various wildlife management and right-of-way maintenance techniques that are incorporated in the plan, while assessing general cost-effectiveness. Although land management to increase wildlife populations has been conducted for many years (Leopold 1933), rights-of-way for powerlines have been seriously managed for wildlife only since the 1950s (Foster 1956; Egler 1957; Niering 1958). Much of the interest in right-of-waY management was due to the availability of herbicides following World War II (Egler 1949), and numerous studies have been conducted to evaluate the various ways to use these chemicals to
M.e. Perry et al.
134
1788 1787
1786
1785
1784
1803
1a01
1800
1799
1802
1783
1782
1781
1779
1778
1777
1776
1775
1774
1773
1796
D Total Mow ~ Strip Mow
ISJ
17S0
Selective Basal
G3 Low Volume Foliar I8a Wildlife Corridor
o Non-Study Area
Fig. 1. Distribution of habitat management techniques used on the 8.5 km (5.3 mile)-long BGE powerline right~of-way as described in the Management Plan.
control unwanted vegetation (Niering and Goodwin 1974; Bramble and Byrnes 1983). Dreyer and Niering (1986) evaluated basal and stem foliar herbicides to selectively eliminate tall-growing trees, and selective basal spraying has been effectively used at Patuxent since 1968 on another powerline right-of-way managed by Potomac Electric Power Company (Fleming 1989; Obrecht et al. 1991). The relationship between powerline right-of-way vegetation and the diversity and abundance of wildlife has been documented in many areas (Gysel 1962; Longcore 1971; Anderson 1979; Meyers and Provost 1979). The influence of landscape-level factors on wintering bird populations in powerline and pipeline right-ofways was evaluated by Pearson (1993). The present study evaluates five major management techniques for right-of-ways in regard to wildlife biodiversity. The objective of this study was to inventory and evaluate seasonal distribution of wildlife (avian, mammalian, and herpetofauna) within the BGE right-of-way in all habitat management types.
TECHNIQUES
The powerline right-of-way was divided into various segments of management techniques based on the Management Plan and using aerial photographs of the area provided by BGE. Five major habitat management techniques have been identified in the Plan and will be studied in this project (Fig. 1). They include two types of mowing (strip and total), two herbicide applications (selective basal spraying and low volume foliar spraying), and establishing wildlife corridors. Wildlife corridor is a special technique obtained by leaVing trees but limiting their height by topping. It simulates the forest
on both sides of the right-of-way and, therefore, acts as a corridor for wildlife moving through the area. The study area for this project included the area between Tower 1778 to 1802 (Table 1). All management techniques were conducted on a tower to tower basis to Table 1. Habitat management techniques used along the BGE powerline right-of-way including the wildlife trapping locations
Tower number
1778-1779 1779-1780 1780-1781 1781-1782 1782-1783 1783-1784 1784-1785 1785-1786 1786-1787 1787-1788 1788-1789 1789-1790 1790-1791 1791-1792 1792-1793 1793-1794 1794-1795 1795-1796 1796-1797 1797-1798 1798-1799 1799-1800 1800-1801 1801-1802
Management tedmiques
Trap site
total mow
total mow selective basal spray selective basal spray selective basal spray strip mow strip mow strip mow low volume foliar spray low volume foliar spray low volume foliar spray low volume foliar spray total mow wildlife corridor wildlife corridor selective basal spray strip mow strip mow selective basal spray total mow wildlife corridor low volume foliar spray total mow low volume foliar spray
yes
yes yes
yes yes
Som~ sections where mowing is .the major management technique also include some spraying to control vegetation in areas hard to reach with mowing equipment.
Optimal management strategies for biodiversity
assist in the experimental design. A total of 24 sections occurred within the study area. The techniques included strip mow (5 sections), total mow (5 sections), selective basal spraying (5 sections), low volume foliar spraying (6 sections), and wildlife corridor (3 sections). In addition to the five major habitat management types that will be studied intensively, there is one area that will not be sampled intensively because of lack of replication. This area is a 2-acre study site used by BGE staff. The study site is being evaluated using a variety of vegetation management techniques to determine effects on the diversity of the plant community (pers. comm., T. Benassi). Bird populations were sampled in 1995-96 by line transect sampling (Burnham et al. 1980) along a transect 'established near the center of the right-of-way. Sampling was conducted by two observers once' a week throughout the year starting at one hour after sunrise. Starting points for both observers were different and were varied so that all habitats were sampled evenly with regard to time of day. The locations of all singing males heard during the breeding season were recorded On a map so that territories could be plotted and breeding bird density could be estimated in each habitat type. In addition to the transect survey, two additional surveys were conducted for nocturnal birds. Woodcock were surveyed at dusk (19:00-21:00) on one night in both March and April. Five observers familiar with the nuptial call and flight of woodcock were assigned to separate sections of the study site so that all areas were surveyed simultaneously. Whip-poor-wills were surveyed similarly between 21:00 and midnight during one night in both May and June. Moon phase was considered when selecting days to increase probability of hearing whip-poor-wills, which are mOre vocal during full moon phases. Mammals were live-trapped during July to November 1996 in one site for each habitat type (Table 1). Sherman live traps (for small mammals) and Hav-a-Hart box traps (for medium-sized mammals) were operated fOr four trap-days per month. All mammals were released on site. Sand plot track sites were established to record tracks of animals that are difficult to trap, such as fox and deer (Perry and Giles 1970). The location of wildlife observed or killed by hunters within right-of-way were recorded and data assembled by staff at the Hunter Control Station in the North Tract of Patuxent. Amphibians and reptiles were sampled at one site for each habitat type with the use of 15.4 m (50 ft) drift fences. Two pitfall traps were constructed at each end and two funnel traps were placed in the middle on each side of the drift fence. At each of the five sites there were two drift fences: one parallel and one perpendicular to the right-of-way. This arrangement was done to intercept animals moving across or along the right-ofway. Each pitfall and funnel trap was numbered to better understand movement of animals by knowing
135
on which side of the fence each animal was caught. The drift fence trapline was opened for five months (July-November 1996) for four trap-days each month. Captured animals were identified, counted, and released on site.
RESULTS
Avian surveys conducted between 1 July 1995 and 30 June 1996 recorded a total of 101 species within the right-of-way or al('ng the edge. Only three species (fish crow, Kentucky warbler, and rock dove) were seen along the edge but not in the right-of-way, whereas, 33 species were seen within the right-of-way but not along the edge (Table 2). However, it should be noted that birds seen or heard along the edge would have been further from the observer, therefore, creating an obvious sampling bias. The eastern towhee had the highest frequency of occurrence (318) followed by the field sparrow (208) and the common yellowthroat (201). The field sparrow had the highest numbers per visit (17.2) followed by the eastern towhee (15.5) and eastern bluebird (13.4). Twelve species that had a total frequency of occurrence of over 100 but were not seen in large numbers «10 birds/visit), included American goldfinch, blue jay, Carolina chickadee, Carolina wren, gray catbird, indigo bunting, northern flicker, prairie warbler, red-bellied woodpecker, red-eyed vireo, tufted titmouse, and white-eyed vireo (Table 2). Three American woodcock were heard conducting courtShip displays along the powerline right-of-way during a special survey on 25 March 1997. One whippoor-will was heard singing in the woods adjacent to the right-of-way on 15 June 1996. These two species were surveyed to fully evaluate diversity of avian species seen or heard in the powerline right-of-way habitats. Several avian species, whose populations are typically low in this area of Maryland, were seen during this study. The Lincoln's sparrow is a migrant in Maryland and was seen twice along the powerline right-ofway during one of the fall surveys. The Henslow's sparrow, although not recorded on the surveys for this study, was observed in May on the North American Migration Count on the BGE powerline right-of-way. The hermit thrush was seen in shrub habitat during the winter on seven different occasions. Seasonal differences in numbers of species using the right-of-way were observed. The greatest number of species recorded in the right-of-way was 80 observed in the fall (Table 3). However, along the edge, the most species seen or heard was 57, which was recorded in the spring. This is most .likely the result of many migrating songbirds using the forest in the spring when males can be heard singing. Fifteen species of birds were seen in numbers greater than 10 birds per visit during at least one season (Table 4). Eight of these species were seen in greatest numbers
M. C. Perry et al.
136
Table 2. Avian species'" recorded during 31 visits along BGE powerline right-of-way during 1 July 1995 to 30 June 1996
Species
Freq*
17 1 80 138 American Goldfinch American Kestrel 5 12 American Redstart 73 American Robin 2 American Tree Sparrow Baltimore Oriole 5 Belted Kingfisher 1 1 BJackpoll Warbler Blk-Ihroated Blue Warbler 3 Blk-throated Green Warbler 2 Black Vulture 1 Black-and-white Warbler 34 Blue-gray Gnatcatcher 43 55 Blue Grosbeak 171 Blue Jay Blue~winged Warbler 1 Broad-winged Hawk 4 Brown Creeper 1 Brown-headed Cowbird 92 Brown Thrasher 41 Canada Goose 4 Carolina Chickadee 136 Carolina Wren 105 Cedar Waxwing 13 Chestnut-sided Warbler 4 ChinU1ey Swift 6 Chipping Sparrow 36 Common Grackle 16 Common Yellowthroat 201 Cooper's Hawk 4 Dark~eyed Junco 69 Downy Woodpecker 45 Eastern Bluebird 179 Eastern Kingbird 86 Eastem Phoebe 27 Eastern Towhee 318 Eastem Wood-Pewee 59 Empidonax Species 7 European Starling 3 Field Sparrow 208 Fish Crow 2 Golden~crowned Kinglet 10 Gray Catbird 171 19 Great Crested Flycatcher Great Horned Owl 1 9 Hairy Woodpecker Hermit Thrush 18 Hooded Warbler 42 I-louse Finch 78 Acadian Flycatcher Accipiter Species American Crow
ROW sum (avg,)
Edge sum (avg,)
Species
Freq"
ROW sum (avg,)
4 (0,1) 1 (0,0) 80 (2,6) 228 (7,4) 8 (0,3) 13 (0,4) 193 (6,2) 2 (0.1) 3 (0,1) 1 (0,0) 1 (0,0) 3 (0,1) 4 (0.1) 2 (0,1) 11 (0,3) 42 (1.4) 80 (2,6) 89 (2,9) 1 (0,0) 4 (0,1) 1 (0,0) 126 (4.1) 40 (1.3) 1 (0,0) 125 (4,0) 116 (3,7) 25 (0,8) 3 (0,1) 3 (0,1) 63 (2,0) 295 (9.5) 334 (10,8) 4 (0,1) 380 (12,3) 30 (1.0) 415 (13,4) 126 (4.1) 27 (0,9) 482 (15.5) 12 (0,4) 6 (0,2) 5 (0,2) 532 (17,2)
15 (0,4)
House Sparrow
1 75 106 9 1 2 1 4 45 85 110 48 31 1 10 73 8 40 28 132 1 113 17 140 8 38 3 4 20 10 1
4 (0.1) 95 (3,1) 149 (4.8)
13 (0,4) 211 (6,8) 2 (0,1) 1 (0,0) 6 (0,2) 19 (0,6) 6 (0,2) 117 (3,8)
117 (3,8) 30 (1.0) 2 (0,1) 61 (2.0) 1 (0,0)
27 (0,9) 11 (0,4) 1 (0,0) 179 (5,8)
18 (0,6) 8 (0.3) 71 (2.3) 21 (0.7) 1 (0,0) 1 (0,0) 4 (0,1) 10 (0,3) 8 (0,3) 1 (0.0) 19 (0,6) 32 (1.0) 4 (0,1) 7 (0.2) 67 (2,2) 52 (1.7) 1 (0,0) 1 (0,0) 9 (0,3) 1 (0,0) 34 (1.1) 20 (0,6) 2 (0.1) 6 (0,2) 40 (1.3) 16 (0.5)
House Wren Indigo Bunting Kentucky Warbler Least Flycatcher Lincoln's Sparrow Louisiana Waterthrush Magnolia Warbler Mourning Dove Northern Cardinal Northern Flicker Norfuem Mockingbird Northern Parula Northern vVaterthrush Orchard Oriole Ovenbird Palm Warbler Pileated Woodpecker Pine Warbler Prairie Warbler Purple Finch Red-bellied Woodpecker Red-breasted Nuthatch Red-eyed Vireo Red-shouldered Hawk Red-tailed Hawk Rock Dove Rose-breasted Grosbeak Ruby~crowned Kinglet Ruby-thr, Hummingbird SaVaIU1ah Sparrow Scarlet Tanager Sharp-shirmed Hawk Song Sparrow SummerTanager Swainson's Thrush Swamp Sparrow Tree Swallow Tufted Titmouse Turkey Vulture White-breasted Nuthatch White-crowned Sparrow White-eyed Vireo White~throated Sparrow Winter Wren Wood Thrush Yellow-bellied Sapsucker Yellow-billed Cuckoo Yellow~breasted Chat Yellow-rumped Warbler Yellow-throated, Vireo
44 5 84 28 2 31 1 173 16 54 2 133 63 1 62 2 33 78 8 32
1 (0,0) 2 (0,1) 1 (0.0) 4 (0.1) 42 (1.4) 102 (3,3) 71 (2,3) 58 (1.9) 6 (0,2) 1 (0,0) 17 (0.5) 6 (0.2) 12 (0.4) 1 (0,0) 25 (0,8) 190 (6,1) 1 (0,0) 13 (0,4) 7 (0.2) 46 (1.5) 3 (0,1) 32 (1.0) 4 (0.1) 33 (1.1) 8 (0,3) 1 (0,0) 14 (0.5) 3 (0.1) 227 (7,3) 28 (0,9) 1 (0.0) 73 (2,4) 1 (0,0) 107 (3.5) 9 (0,3) 6 (0.2) 2 (0.1) 136 (4,4) 195 (6,3) 1 (0,0) 1 (0,0) 2(0,1) 1 (0.0) 88 (2,8) 4 (0,1) 5 (0,2)
Edge sum (avg.)
1 (0,0) 10 (03) 9 (0,3)
1 (0.0) 14 (0,5) 22 (0,7) 64 (2.1) 25 (0,8)
86 (2.8) 29 (0,9) 21 (0,7) 9 (0,3) 121 (3.9) 22 (0,7) 178 (5,7) 3 (0.1) 2 (0,1) 1 (0,0) 1 (0.0) 1 (0,0)
35 (1.1)
10 (0,3) 2 (0.1) 2 (0.1) 151 (4,9) 2 (0.1) 52 (1.7) 20 (0.6)
83 (2.7) 40 (1.3) 1 (0,0) 9 (0,3) 32 (1.0)
*Frequency represents the total number of times the species was recorded 'at least once within any section during any visit. The sum is the total individuals for all sections and all Visits. Average is total divided by 31 visits.
Optimal management strategies for biodiversity Table 3. Bird species recorded"by season* along the powerline right-ot-way (ROW) and the edge ot the right-ot-way during 31 visits, 1 July 1995 to 30 June 1996
Table 5. Species of mammals captured* on the BGE powerline right~of~waybetween 16 July and 15 November 1996 Species
Summer
Fall
Winter
Spring
51 46
80 46
31 14
67 57
137
Totai
Sites 1
ROW Edge
*Summer "'" 1 June-15 August; Fall "'" 16 August"':'30 November; Winter"'" 1 December-29 February; Spring::::; 1 March-31 May.
per visit in the fall and five species were seen in greatest numbers per visit in the summer (Table 4). The American robin was seen in greatest numbers per visit in the winter and the brown-headed cowbird was recorded in greatest numbers in the spring. Nine species of mammals were captured within the right-of-way during the five-month trapping period (16 July-15 November 1996) in live box traps or pitfall traps (Table 5). The white-footedinouse (Peromyscus leucopus) was the most numerous of the small mammals captured. The meadow jumping mouse (Zapus hudsonius) and the masked shrew (Sorex cinereus) were most frequently captured at Site 2, the wettest of the five sites. Among the medium-sized mammals only one opossum and eight raccoons were captured. The trapping rate for these two species is about half that obtained on forested wetlands during another study at Patuxent Research Refuge (Perry et al. 1996). The gray fox (Urocyon cinereoargenteus), red fox (Vulpes fu1va), and groundhog (Marmota monax) were seen along the rightof-way during the study, but were not captured. Whitetailed deer (Odocoileus virginianus) were frequently seen on the powerline right-of-way and numerous deer were killed by hunters along the right-of-way during
Opossum Masked Shrew Short-tailed Shrew EastemMole Raccoon White-footed Mouse Meadow Vole Pine Vole Vole species Meadow Jumping Mouse Total
1 5 4 1 8 17 2 2 1 5
46
5
2
3
3 1 1 4 1 1
4
1 2 3 3
1 5
1
15
6 1 1
1 1
4
6
5
6
11
8
'Trap days totalled 300 for Hav-A-Hart traps, 487 for Sherman live traps, and 100 for drift fences.
the hunting season. The right-of-way has traditionally been a preferred hunting area for hunters at Patuxent. Twelve species of amphibians were captured within the powerline right-of-way during the trapping period (16 July-15 November). The green frog (Rana clamitans) was the most frequently captured amphibian representing 45 of the total 145 individual amphibians that were captured (Table 6). The chorus frog (Pseudoacris triseriata) was heard calling during the spring in numerous wet areas of the right-of-way, but was not captured in the traps. Three species of salamanders, but only five individuals, were captured. Six species of reptiles and 16 individuals were captured within the right-of-way (Table 6). All reptiles
Table 4. Most abundant species of birds recorded along the BGE powerline right-of~wayduring visits 1 July 1995 to 30 June 1996* Species Americar\. Goldfinch American Robin Brown~headed Cowbird Common Grackle Common Yellowthroat Dark-eyed Junco Eastern Bluebird Eastern Kingbird Eastern Towhee Field Sparrow Gray Catbird Indigo Bunting Prairie Warbler Song Sparrow White~thr. Sparrow
Summer 61 (10.2) 6 (1.0) 28 (4.7) 86 (14.3) 45 (7.5) 69 (11.5) 110 (18.3) 68 (11.3) 71 (11.8) 75 (12.5) 72 (12.0)
Fan
Winter
125 (10.4) 71 (5.9) 3 (0.3) 295 (24.6) 126 (10.5) 254 (21.2) 270 (22.5) 10 (0.8) 242 (20.2) 263 (21.9) 92 (7.7) 29 (2.4) 14 (1.2) 144 (12.0) 172 (14.3)
3 (0.8) 98 (24.5)
64 (16.0) 35 (8.8)
61 (15.3)
15 (3.8) 16 (4.0)
Spring 39 (4.3) 18 (2.0) 95 (10.6) 122 (13.6) 62 (6.9) 65 (7.2) 47 (5.2) 130 (14.4) 140 (15.6) 48 (5.3) 45 (5.0) 104 (11.6) 68 (7.6) 7 (0.8)
*Numbers are total individual birds seen and average number per visit in parentheses, The 31 visits included 6 in summer (1 June-15 August), 12 in fall (16 August-30 November), 4 in winter (1 December-29 February), and 9 in spring (1 March-31 May).
M. C. Perry et at.
138
Table 6. Species of amphibians and reptiles captured* on the 8GE powerline right~of~way between 16 July and 15 November 1996
Total
Sites
1 Amphibians Marbled Salamander
Red-spotted Newt Four-toed Salamander
American Toad Fowler's Toad Northern Cricket Frog Spring Peeper
Bull Frog Green Frog Wood Frog Southern Leopard Frog Pickerel Frog Total
Reptiles Northern Fence Lizard Six-lined Racerunner Five-lined Skink Eastern Garter Snake Eastern Hognose Snake Northern Black Racer Total
1 2 2 23 21 23 4 3 45 1 8 12 145
4 1 1 5 2
2
3
4
5
7 2 2
2 2 2
1 5 1
1 5 1
1
2
27
2 2 6 1 4 3 1 6
2 1
2
3
1
3
7
26
48
30
28
2
2
6 16
2 15 1
13
1 1 1
4
3
2 1
16
4
0
6
1
1
4
2
*Trap days for drift fence was 100.
captured are species typically found in fairly dry habitat, which was where they were captured within the powerline right-of-way. No reptiles were captured at site 2, the wettest site.
the right-of-way habitat to be homogenous. Differences noted among wildlife species observed or captured were best explained by physical or hydrological features, rather than with management techniques. Past management practices of the right-of-way also appeared to be a factor in wildlife numbers. For example, robin abundance during winter seemed strongly associated with large numbers of holly (Ilex opaca) trees on the powerline right-of-way (especially between towers 1786-1790). Holly trees, which have been protected for many years on the right-of-way, provide excellent food and cover to the robin, a major winter migrant in Maryland. Ii, future years, as the new techniques result in more alteration of the right-of-way habitats, it is expected that greater differences in the wildlife populations will be recorded. Attention should be given, however, to species that may potentially affect biodiversity adversely in the future. The brown-headed cowbird was recorded in high numbers in the spring and this could reflect high parasitism on other species whose populations are low. Nest surveys should be conducted to evaluate the extent of the problem and if nest parasitism differs among management techniques. The exotic vine, mile-a-minute weed (Polygonum perjoliatum), was found in several areas of the right-of-way and could increase its distribution in the future. This fast growing plant has the potential to spread throughout the rightof-way and negatively impact native plants. When differences in habitats and species using these habitats are noted in future years as a result of management techniques, researchers will be able to advise the managers of optinmm techniques to use to benefit biodiversity along the right-of-way. The findings of this study indicate that the powerline right-of-way is providing habitat to a large number of wildlife species and, hopefully, will continue to be important habitat in the future.
DISCUSSION ACKNOWLEDGEMENTS
The number of bird, mammal, amphibian, and reptile species captured or seen along the powerline right-ofway during 1995-96 reflects the relatively high biodiversity of these habitats created and maintained by humans. Although no rare species of animals were recorded during this study, more intensive sampling of the flora and fauna in the future will probably increase the species list and possibly add some rare species to the list. The present management plan conducted by BGE in cooperation with the Patuxent Research Refuge staff is flexible and can easily accommodate the protection of unique habitats or rare species. Because the right-of-way was managed with similar techniques (mostly low volume foliar spray) from 1971 to 1995, there were few differences in the wildlife species composition or numbers among the 26 sections. The construction activities during 1994-95 also caused
Assistance with the experimental design was obtained from T. Benassi, C. Devine, J. Hatfield, and H. Obrecht, III. Establishment of drift fences was done by B. Bauman, J. Cowan, S. Pugh, and S. Tanata. Assistance with data entry and analyses was obtained from G. Gough, L. Loges, and C. Sibrel. K. Boone and L. Lammons assisted with graphics and word processing. Drafts of this manuscript were reviewed by D. Dawson, H. Obrecht, T. Benassi, and two anonymous reviewers.
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Optimal management strategies for biodiversity
Bramble, W.e. and W.R. Byrnes.. 1983. Thirty years of research on development of plant cover on an electric transmission right~ of-way. Journal of Arboriculture, 9: 67~74. Burnham, KP., D.R. Anderson, and J.L. Laake. 1980. Estimation of density from line transect sampling of biological populations. Journal OF Wildlife Management, 72: 202. Dreyer, G.D. and W.A. Niering. 1986. Evaluation of two herbicide techniques on electric transmission rights-of~way: development of relatively stable shrublands. Environmental Management, 10(1): 113-118. Egler, F.E. 1949. Right-ai-way maintenance by plant commnnity management. Aton Forest, Norfolk, COlU1ecticut. 19 pp. Egler, F.E. 1957. Right-ol-way and wildlife habitat: progress report. Transaction North American Wildlife Conference, 22:
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BIOGRAPHICAL SKETCHES Matthew C. Perry Pafuxent Wildlife Research Center, 11410 American Holly Drive, Laurel, MD 20708, USA B.S. University of Rhode Island; M.s. Virginia Polytechnic Institute, PhD University of Maryland. Peter C. Osenton Patuxent Wildlife Research Center, 11410 American Holly Drive, Laurel, MD 20708, USA B.S. University of Rhode Island. Frederick W. Fallon Patuxent Wildlife Research Center, 11410 American Holly Drive, Laurel, MD 20708, USA A.B. Harvard College, M.S. University of South Florida, Ph.D. University of South Florida. lane E. Fallon Patuxent Wildlife Research Center, 11410 American Holly Drive, Laurel, MD 20708, USA B.S. Michigan State University, M.S. Ohio State University.
