Northeastern Naturalist Vol. 22, No. 1 S.R. Morris and B.A. Stumpe 2015 95 2015 NORTHEASTERN NATURALIST 22(1):95–105 Limited Impact of a Small Residential Wind Turbine on Birds on an Off-Shore Island in Maine Sara R. Morris1,2,* and Brynne A. Stumpe1 Abstract - We studied the impact of a small, residential wind turbine on birds on Appledore Island, ME, to augment the limited published data on avian fatalities due to residential turbines. We conducted mortality and behavioral surveys of birds flying in the vicinity of the turbine. We did not detect any turbine-related fatalities during twice-daily surveys from fall 2007 to spring 2012, and we have only two anecdotal reports of collision events. Behavioral observations showed that the majority of birds flew below the turbine propeller (95.5%) vertically and near the turbine (53.4%) horizontally. Our behavioral surveys indicated that birds were often seen close to the monopole, but were less likely to be detected near the turbine blades compared to areas more distant from the blades. Furthermore, birds perching on and around the monopole structure provided additional anecdotal evidence of birds not avoiding the vicinity of the wind turbine. Our findings suggest a limited impact of this residential wind turbine on birds. However, we advise carefully choosing the location of a wind turbine so as to minimize potential impacts to avian populations; the turbine on Appledore Island was constructed only after extensive consideration of the possible impacts on birds at this site. Introduction Wind turbines and other towers are known to cause avian mortality (e.g., Erickson et al. 2001, Gehring et al. 2011, Hüppop et al. 2006, Johnson et al. 2002, Kuvlesky et al. 2007). The increase in wind-power development over the last two decades necessitates understanding how wind turbines affect birds and bird populations (e.g., Desholm 2009, Drewitt and Langston 2006, Kuvlesky et al. 2007). In most studies of avian mortality caused by wind turbines, observers search for carcasses around the turbines (e.g., Hüppop et al. 2006). Critics have suggested several problems with this method (reviews in Drewitt and Langston 2006, Morrison 2002). First, most of these studies involve surveys once every 7–10 days. Because scavengers can remove carcasses from the search area before they are found, search frequency should be adjusted to disappearance rate (Krijgsveld et al. 2009, Morrison 2002, Smallwood 2007, Smallwood et al. 2010); scavenger effects are a particular concern when sampling is relatively infrequent. Second, all carcasses may not be found, especially if there are inexperienced searchers, if there is high/coarse vegetation, or if the carcasses are outside the radius being searched. Risk of collision varies by species, location, and time. Raptors may be at a higher risk than many other landbirds because of their foraging and flight behavior 1Department of Biology, Canisius College, 2001 Main Street, Buffalo, NY 14208. 2Shoals Marine Lab, Cornell University, Ithaca, NY 14850. *Corresponding author - morriss@ canisius.edu. Manuscript Editor: Peter Paton Northeastern Naturalist 96 S.R. Morris and B.A. Stumpe 2015 Vol. 22, No. 1 (Barrios and Rodriguez 2004, Hoover and Morrison 2005). Raptors accounted for >40% of avian mortality at the Altamont Pass Wind-Resource Area in California (Smallwood and Thelander 2008). At this site, bird activity peaked during winter, although it varied among species (Smallwood et al. 2009). In a study of wind farms in the Netherlands, Krijgsveld et al. (2009) found that local species were more likely to be killed than passage migrants and diurnal species were more likely to be killed than nocturnal species. In Belgium, Stienen et al. (2008) found much higher rates of mortality among male than female Sterna hirundo L. (Common Terns), which was mostly due to high flight intensity as well as differences in behavior, particularly during the incubation phase of the breeding cycle when females do more incubation and males often provide food to females. In addition to being a known source of mortality among birds, wind turbines can also cause behavioral changes in avian species. Birds in flight that see a turbine can avoid the object and thus may change their flight patterns. Desholm and Kahlert (2005) found that significantly fewer geese and ducks flew into the vicinity of a large offshore wind farm compared to the number flying in the area prior to construction. Turbines could pose problems to migrant birds that may use slightly different routes each year and thus be unfamiliar with specific turbines. Additionally, turbines may be an obstacle for breeding birds that must navigate around them to return to their nest sites, especially when feeding young. During the summer of 2007, the Shoals Marine Lab installed a residential wind turbine on Appledore Island, ME. Because Appledore Island supports a large breeding colony of Larus argentatus Pontoppidan (Herring Gull) and L. marinus L. (Great Black-backed Gull) and is the site of a long-term songbird-migration banding station, the permitting agents expressed concerns about the turbine’s impact on local birds. The goal of this project was to assess how this residential wind turbine might affect birds on Appledore Island, ME. Specifically, we investigated whether the turbine (1) caused avian mortality and/or (2) whether birds seemed to be avoiding the vicinity of the turbine. Field Site Appledore Island, ME, is a 33.6-ha island located approximately 14 km southeast of Portsmouth, NH. The dominant habitats on the island are coastal scrub-shrub, grassy field, and open rock. Morris et al. (1994, 1996) and Suomala et al. (2010) summarized the flora of the island. Seabirds that breed on the island include Herring and Great Black-backed gulls, Cepphus grille L. (Black Guillemot), and Somateria mollissima L. (Common Eider). The two gull species are the most numerous breeding birds on the island, with over 1000 breeding pairs (Eastwood et al. 2009, Ellis et al. 2007). The most common breeding songbirds are Tachycineta bicolor Vieillot (Tree Swallow), Hirundo rustica L. (Barn Swallow), Setophaga petechia L. (Yellow Warbler), Geothlypis trichas L. (Common Yellowthroat), and Melospiza melodia Wilson (Song Sparrow) (Eastwood et al. 2009). During the 1980s and 1990s, an active heronry included breeding Egretta thula Molina (Snowy Egret), Nycticorax nycticorax L. (Black-crowned Night-Heron), Plegadis falcinellus L. (Glossy Ibis), Northeastern Naturalist Vol. 22, No. 1 S.R. Morris and B.A. Stumpe 2015 97 Egretta caerulea L. (Little Blue Heron), and Ardea alba L. (Great Egret). However, the numbers of these species have decreased through the 2000s. During spring and fall migration, more than 100 species of migrant birds use Appledore Island as a stopover site (Morris et al. 1994, 1996). For approximately 5 weeks each spring and fall since 1990, a migration banding station has regularly monitored migrant landbirds during stopover. Wind turbine During July 2007, Northeast Wind Energy (East Killingly, CT) erected a 24-m self-supporting, tilt-down monopole on Appledore Island. In a series of recommendations to decrease the impact of wind turbines on birds, Manville (2005) noted that a monopole was preferable to a lattice or guyed support structure. The monopole supported a Bergey Windpower 7.5-kW Excel battery-charging turbine. Each blade of the turbine measured 3.3 m, and the entire rotor had a 7-m diameter. To reduce the potential impact on birds, one black turbine blade provided contrast to the two normal white blades. The turbine was placed on an open, rocky area in the northern portion of the island. This area was not in close proximity to the high-density areas of the gull colony, but rather was in an area with only a limited number of gull nests (fewer than 10 nests were within 5 m of the monopole). The turbine was located 25–90 m from mist nets used for the migration banding station. Methods Mortality surveys Mortality surveys at the wind turbine began on Appledore Island during the 2007 fall migration season and continued during all subsequent spring and fall migratory seasons through spring 2012. During the banding season (~10 May–10 June for spring migration and ~15 August–20 September for fall migration), banding-station personnel searched for evidence of avian mortality around the turbine twice a day: once at sunrise (which varied seasonally from 04:50 to 07:00) and a second time between 14:00 and 16:00. During each survey, observers searched all open areas within 30 m of the turbine—about 25% of this area was open enough for searching depending on the season—and all trails within 60 m of the turbine. Additionally, the staff of the Shoals Marine Lab reported any possible avian collisions with the turbine and any dead birds in the vicinity of the turbine to the banding-station personnel. To test the observers’ abilities to find birds, the bander in charge of the station or the Assistant Director of the Shoals Marine Lab occasionally placed carcasses in the search area to determine how long it took observers to find a known carcass. One carcass of each of the following species was placed in the survey area: Herring Gull, Megaceryle alcyon L. ( Belted Kingfisher), Vireo olivaceus L. (Red-eyed Vireo), Dumetella carolinensis L. (Gray Catbird), Setophaga americana L. (Northern Parula), and Haemorhous purpureus Gmelin (Purple Finch). Carcasses were salvaged on the island as recent fatalities from collisions with windows, as part of the banding-station activities, or after a territorial dispute. A single bird was placed Northeastern Naturalist 98 S.R. Morris and B.A. Stumpe 2015 Vol. 22, No. 1 at any one time, generally only once per year, and observers were not aware of these detection tests. Additionally, the dead birds were left in place to monitor possible scavenging of carcasses at this site. Behavior surveys Observers collected data on bird flight in the vicinity of the turbine during fall 2009 and spring 2010. Observers sat in an open area 22 m from the base of the turbine. In the spring, the gulls nesting closest to the observer occasionally left their nests when the observer arrived, but returned to their nests prior to observations— usually within 1 minute. Observation periods ranged from 15 to 60 min. During behavioral observations, we identified each bird to group (e.g., gull, tern, sparrow) or species, documented its location relative to the turbine, and noted the Figure 1. Illustration of residential wind turbine and the vert ical and horizontal levels used to characterize where birds were flying during behavioral observations on Appledore Island, ME. For vertical levels above (VA1–VA3) and below (VB1–VB3) the propeller, the bird was: (1) less than 1/3 of the monopole from the propeller hub (less than 8 m), (2) 1/3–2/3 of the monopole from the propeller hub (8–16 m), or (3) >2/3 of the monopole from the propeller hub, but no more than the height of the monopole (16–24 m). For horizontal levels, the bird was: (H1) less than 1/6 of the monopole height from the propeller hub (less than 4 m), (H2) 1/6–1/3 of the monopole height from the propeller hub (4–8 m), or (H3) >1/3 of the monopole height from the propeller hub, but less than 1/2 the height of the monopole (8–12 m). Northeastern Naturalist Vol. 22, No. 1 S.R. Morris and B.A. Stumpe 2015 99 time. In addition to recording whether birds were flying above or below the turbine, observers determined relative distance of the birds from the turbine (Fig. 1). We divided areas above (VA) and below (VB) the wind turbine into 3 vertical levels: the bird was at a distance less than 1/3 (less than 8 m), 1/3 to 2/3 (8–16 m), or >2/3 (16–24 m, but no higher) the height of the monopole from the propeller hub. This system used 6 categories: 3 above (VA1-3) and 3 below (VB1-3) the propeller hub (Fig. 1). We also recorded the horizontal distance from the turbine. Again, we created 3 categories, with each third of the monopole height used as the diameter of a cylinder centered on the monopole (Fig. 1). Thus, our 3 horizontal categories indicated the following distances: the bird was less than 1/6 of the monopole height from the propeller hub (less than 4 m), 1/6 to 1/3 (4–8 m), or >1/3 of the monopole heightfrom the propeller hub, but less than 1/2 the height of the monopole (8–12 m). Statistical analyses We used Pearson chi-square tests to determine if the distribution of birds was even among all levels during behavioral observations. We used likelihood-ratio chi-square tests to compare distributions between waterbirds and landbirds. We used SYSTAT v13 for all statistical tests (Systat Software, San Jose, CA). Results Mortality surveys We completed surveys on 327 days from fall 2007 through spring 2012 and found no turbine-related fatalities during our twice-daily surveys. Observers found 5 of the planted carcasses during the first survey after each carcass was placed. Observers did not find the 6th planted carcass, which was the Northern Parula. However, observers had only one opportunity to find it because the carcass was planted on the last afternoon of the season; therefore, we also excluded it from the scavenging data below. At this site, we did not have evidence of scavenging of carcasses; all planted carcasses remained in place for the remainder of the banding season and did not disappear (n =5, mean = 8.6 ± 6.8 days, range = 2–19 days). We removed the carcasses from the area at the end of the banding season. Although we never documented a turbine-related mortality during our twicedaily surveys, we had two anecdotal accounts of collisions between birds and the turbine during the 10 seasons studied. In fall 2011, one of the Shoals Marine Lab staff members (D. Broman, pers. comm.) heard a strike and saw a Herring Gull fall to the ground after colliding with a turbine blade, although no carcass was ever found, presumably because of high shrubs and low trees in the area. During spring 2012, the banders heard a loud metallic sound that was likely a bird colliding with the turbine, although no one witnessed a collision because the banders were at the netting location and could not see the turbine. Four days later, a bander found a severed Herring Gull wing ~75 m from the turbine in shrubs outside the mortality-survey area. Behavior surveys We completed 21.5 h of behavior surveys between 16 August 2009 and 9 June 2010, during which we observed 1531 birds of 16 species in the vicinity of the Northeastern Naturalist 100 S.R. Morris and B.A. Stumpe 2015 Vol. 22, No. 1 tower (Table 1). The average number of birds observed in our survey area was 67.6 ± 39.4 per hour. Of the birds seen, 71.9% were waterbirds and 28.1% were landbirds. Gulls accounted for 71.0% of all the birds. The species seen most often were Herring Gulls (55.7% of all birds seen), Great Black-backed Gulls (14.2%), and swallows (12.9%). The vast majority of birds (95.5%) flew below the level of the turbine propeller (χ2 = 1267, df = 1, P < 0.001). In our observations of vertical levels, we found that the majority (73.4%) of birds flew below the turbine propeller at level VB3, which was closest to the ground and farthest from the propeller (χ2 = 3683, df = 5, P < 0.001). In the horizontal-level observations, we found that the majority (53.4%) of birds flew at level H1, which was closest to the propeller (χ2 = 326, df = 2, P < 0.001). Many (45.5%) birds were flying at level H1VB3, which was close to the ground but close to the turbine horizontally (Fig. 2). When comparing landbird and waterbird categories, we observed the majority of both groups flying below the propeller in level VB3, which was closest to the ground, although we observed a greater proportion of waterbirds in that level (waterbirds: 80.1%; landbirds: 56.4%; χ2 = 127, df = 5, P < 0.001; Fig. 2). For the horizontal positions, we observed the majority (62.0%) of waterbirds flying at level Table 1. Bird species identified in the vicinity of a residential wind turbine during behavioral surveys in fall 2009 and spring 2010 on Appledore Island, ME. Common name Scientific name # observed Double-crested Cormorant Phalacrocorax auritus (Lesson) 5 Mallard Anas platyrhynchos L. 3 Unidentified duck Family Anatidae 4 Herring Gull Larus argentatus Pontoppidan 853 Great Black-backed Gull Larus marinus L. 217 Unidentified gull Larus sp. 17 Unidentified tern Sterna sp. 1 Ruby-throated Hummingbird Archilochus colubris (L.) 1 Downy Woodpecker Picoides pubescens (L.) 1 Eastern Kingbird Tyrannus tyrannus (L.) 3 Tree Swallow Tachycineta bicolor (Vieillot) 3 Barn Swallow Hirundo rustica (L.) 144 Unidentified swallow Family Hirundinidae 50 Gray Catbird Dumetella carolinensis (L.) 8 Cedar Waxwing Bombycilla cedrorum Vieillot 32 Common Yellowthroat Geothlypis trichas (L.) 1 Magnolia Warbler Setophaga magnolia (Wilson) 1 Yellow Warbler Setophaga petechia (L.) 7 Unidentified warbler Family Parulidae 9 Unidentified sparrow Family Emberizidae 1 Red-winged Blackbird Agelaius phoeniceus (L.) 5 Common Grackle Quiscalus quiscula (L.) 148 American Goldfinch Spinus tristis (L.) 15 Unidentified landbird 2 Total 1531 Northeastern Naturalist Vol. 22, No. 1 S.R. Morris and B.A. Stumpe 2015 101 Figure 2. Numbers of birds observed relative to a small, residential wind turbine on Appledore Island, ME, during behavioral observations made in fall 2009 and spring 2010. The 3 panels show A. all birds, B. waterbirds, and C. landbirds. Black bars represent horizontal level 1 (H1; less than 4 m from the propeller hub), white bars horizontal level 2 (H2; 4–8 m from the propeller hub), and grey bars horizontal level 3 (H3; 8–12 m from the propeller hub). The majority of birds flew at level H1VB3, which was close to the ground, but close to the turbine horizontally. However, the majority of landbirds flew at level H2VB3, which was close to the ground and horizontally 1/3–2/3 the length of the monopole to the turbine hub. Northeastern Naturalist 102 S.R. Morris and B.A. Stumpe 2015 Vol. 22, No. 1 H1, closest to the propeller, but the highest proportion (43.2%) of landbirds were observed at level H2, which was 1/3–2/3 the height of the monopole from the propeller hub (χ2 = 119, df = 2, P < 0.001). Herring Gulls were most often (59.0%) seen at H1VB3 (horizontally close to the turbine, and vertically close to the ground). Great Black-backed Gulls were also seen a majority (44.9%) of the time at H1VB3, but swallows were seen most often in H2, about equally above (H2VA3: 19.3%) and below (H2VB3: 18.3%) the propeller. In addition to completing behavioral observations, we also noted some bird behavior during mortality surveys. On 107 days during fall migration, we recorded whether there were birds perched on or around the scaffolding at the base of the turbine. On 72% of these days, gulls were seen perching on the scaffolding or standing near the base of the turbine. Discussion During 5 years of operation, we did not find any tower-related bird mortality at this residential-sized wind turbine during our twice-daily mortality surveys, and we only had two anecdotal accounts of birds colliding with the turbine. Smallwood (2007) reported that typical detection rates range from 80% of large non-raptors to 51% for small birds. Because we found most detection-test carcasses immediately, and those birds remained on site until the end of the banding season, the low collision rate we documented was not due to low searcher-efficiency or a high scavenging rate at this site. However, the large area that could not be effectively searched due to vegetation coverage could have resulted in some undetected fatalities. Nonetheless, the low number of documented collision victims suggests this turbine had a low impact on Appledore Island birds. This finding is particularly important because several hundred Herring and Great Black-backed Gulls breed on Appledore Island, and several pairs bred each year near the base of the turbine— there were typically 5–10 pairs within 5 m of the turbine base. Furthermore, Appledore Island is a regular stopover site for thousands of migrant landbirds (Morris et al. 1996). The type and height of the turbine-support structure is likely to affect the risk of avian mortality. In a study of communication towers, Gehring et al. (2011) found that the number of avian fatalities at unguyed medium-height towers was much lower than at guyed medium-height towers, and that the number of avian fatalities at guyed medium height-towers was much lower than at guyed tall towers. Thus, we expected that the use of a short, unguyed monopole for this turbine would have minimal impact on bird mortality. This result was critical because the breeding gulls are likely to fly at lower levels as they return to their nest sites during the spring and summer, a pattern we observed around this monopole. During our behavioral surveys, we documented numerous birds flying in the vicinity of the turbine. Most of the birds we saw were flying close to the ground away from the propeller but horizontally close to the turbine tower. Thus, they were not flying near the propeller of the turbine, but there was no evidence of avoidance of the vicinity of the monopole during local movements. A study of bird behavior Northeastern Naturalist Vol. 22, No. 1 S.R. Morris and B.A. Stumpe 2015 103 on a wind farm in southwestern Minnesota also found that the majority of birds (>70%) flew below the level of the turbine blades (Osborn et al. 1998). However, that study suggested that birds were avoiding areas with large turbines (37-m tower, 33-m blade diameter; Osborn et al. 1998) compared to similar areas without turbines, and also found that birds often adjusted their flight patterns around running turbines and typically did not make adjustments when flying near non-running turbines. Our data did not address avoidance behavior on Appledore Island. An additional impact of wind turbines may be that birds simply avoid an area. For example, at a wind farm in California, birds rarely perched on operating turbines and spent less time flying within 50 m of turbines as their operation increased (Smallwood et al. 2009). However, in our study, birds regularly perched on and near the operating turbine (>70% of the dates surveyed). We also observed several gulls nesting within 5 m of the turbine on Appledore Island; in Belgium, Common Terns nested >30 m from commercial wind turbines (Everaert and Stienen 2007). Although the density of the gulls near the turbine on Appledore Island was less than half that of the densest areas of the colony, it was typical of the other areas with similar vegetation, and the presence of several nests each year suggests that birds are not avoiding this turbine area. From our data, we conclude that a small, residential wind turbine had limited effects on birds. We base this finding on the lack of mortality documented during surveys, only limited anecdotal evidence of collisions, a large number of birds flying close to the monopole during behavioral observations, and regular observations of birds perching on and nesting close to the tower. The turbine design for Appledore Island included several features intended to limit the effects on birds including a monopole as the support structure and one black blade to produce contrast to the white blades for increased visibility. Furthermore, the exact location of the Appledore Island turbine was chosen after extensive study of the birds at this site to avoid the densest areas of breeding seabirds and areas of high rates of bird movement (passage and soaring); thus, our study may also demonstrate the importance of carefully choosing a location for a turbine to avoid negative effects on birds and bird behavior. Acknowledgments We are grateful to Canisius College and the Shoals Marine Lab for their continued support of the Appledore Island Migration Station (AIMS). We would like to thank M. Barber, L. Burton, K. Covino, D. Holmes, T. Holmes, J. Jacobs, D. Nally, L. Seitz, M. Stauffer, R. Suomala, A. Thiede, and S. Walsh for their assistance in collecting behavioral observations and all the AIMS volunteers for completing the mortality surveys. D. Fatunmbi generously provided the illustration for Figure 1. R. Hansen prepared the island for the turbine and planned the location and the turbine structure to have minimal impacts on birds. Canisius College provided funding for B.A. Stumpe through the Canisius Earned Excellence Program. Two anonymous donors to the Canisius Laboratory of Avian Biology also funded B.A. Stumpe. This paper is contribution number 19 of the Appledore Island Migration Station and number 178 of the Shoals Marine Lab. Northeastern Naturalist 104 S.R. Morris and B.A. Stumpe 2015 Vol. 22, No. 1 Literature Cited Barrios, L., and A. Rodriguez. 2004. Behavioural and environmental correlates of soaringbird mortality at on-shore wind turbines. Journal of Applied Ecology 41:72–81. Desholm, M. 2009. Avian sensitivity to mortality: Prioritizing migratory bird species for assessment at proposed wind farms. Journal of Environmental Management 90:2672–2679. Desholm, M., and J. Kahlert. 2005. Avian collision risk at an offshore wind farm. Biology Letters 1:296–298. 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