2009 Spring, Summer, and Fall Avian and Bat Surveys


Title: 2009 Spring, Summer, and Fall Avian and Bat Surveys
Publication Date:
December 01, 2009
Pages: 109
Sponsoring Organization:

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Stantec Consulting (2009). 2009 Spring, Summer, and Fall Avian and Bat Surveys. Report by Stantec Consulting. pp 109.

During spring, summer, and fall 2009, Stantec Consulting (Stantec) conducted field surveys of bird and bat migration and breeding bird activity at the Groton Wind Project area in Groton, New Hampshire (Project). The surveys are part of the planning process by Groton Wind, LLC (Groton Wind) for a proposed wind Project, which will include the erection of up to 25 wind turbines and associated infrastructure (e.g., access roads, transmission lines, electrical substation, turbine lay-down/staging area, and operations and maintenance building). The turbines will likely be 2.0 Megawatt (MW) machines mounted on tubular steel towers with an approximate hub height of 78 meters (m; 256 feet [']) and a rotor diameter of 87 m (285'). The proposed turbines would have a maximum height of approximately 121 m (399').


This report details results of a late spring/early summer 2009 breeding bird survey, spring and fall 2009 diurnal raptor surveys and a fall 2009 acoustic bat survey, all of which provide information on seasonal migration activity and patterns as well as local breeding bird activity in the Project area during a period from late March through October 2009.


Breeding Bird Survey


The late spring/early summer 2009 breeding bird survey focused on documenting the occurrence of species of conservation concern, but considered all avian species visually or acoustically detected in the Project area. The survey provides baseline data for the species present in the Project area, their abundance, as well as the community structures among the different habitats present. Stantec biologists conducted breeding bird point-count surveys during two separate visits to the Project area. One round of breeding bird surveys was conducted in early to mid-June (June 10, 11 and 16), and one in mid to late June (June 17, 18 and 27). There were a total of 21 breeding bird point-count locations surveyed within the Project area and an additional 10 locations surveyed within the control areas.


A total of 34 species were observed within the Project area during point-count surveys, and two additional species, American robin (Turdus migratorius) and ruffed grouse (Bonasa umbellus), were observed incidentally between survey points, for a total of 36 species detected in the vicinity of the Project area. Within both the Project area and control areas, the most commonly observed birds included ovenbird (Seiurus aurocapillus) , black-throated blue warbler (Dendroica caerulescens), hermit thrush (Catharus guttatus) and dark-eyed junco (Junco hyemalis). There were no state-listed endangered, threatened or special concern species, or species of federal concern observed during the point-count surveys. A total of 33 species were observed within the control areas during the point-count surveys. Five additional species, [wood thrush (Hylocichla mustelina), eastern wood-pewee (Contopus virens), eastern phoebe (Sayornis phoebe), American robin and veery (Catharus fuscescens)] were observed incidentally between survey points, for a total of 38 species detected in the vicinity of the control areas. Using the results of the point-count surveys only, there were 27 species in common between the Project area and control areas.


Diurnal Raptor Surveys


The 2009 raptor migration studies were conducted to investigate use of the proposed Project area by migrating raptors and their flight behaviors. Spring and fall 2009 diurnal raptor surveys were based on Hawk Migration Association of North America (HMANA) methods (HMANA 2007). Spring surveys occurred from late March through late May with the initial survey dates intended to target early migrants such as golden eagles (Aquila chrysaetos). Fall surveys occurred from late August to late October, including the initial time period when outbound cool weather migrants such as golden and bald eagles begin to migrate. For several of the survey days, simultaneous surveys were coordinated by two observers located at different locations to maximize the amount of the Project area visible by observers.


Spring raptor migration surveys were conducted on 11 days from March 26 to May 23, 2009. Including those birds seen within and outside of the Project area, a total of 175 raptors representing 11 species were observed. Turkey vulture (Cathartes aura, n=99) and red-tailed hawk (Buteo jamaicensis, n=33) were the most frequently observed species. Spring passage rates ranged from 0 to 10 birds/h, with a seasonal average of 1.40 birds/hr. Seventy six birds observed (43%) were within the Project boundary. Of theses, a total of 43 birds, 25 percent of all observations, occurred in the Project area below the maximum rotor-swept zone of the proposed turbines.


The fall raptor survey occurred on 10 days between August 24 and October 26. A total of 696 raptor observations representing 14 species were observed during the fall 2009 surveys. Fall passage rates ranged from 0.56 to 15.81 birds/hr, with an average of 4.35 birds/hr. During the fall raptor survey, broad-winged hawks (Buteo platypterus), red- tailed hawks, turkey vultures, and sharp-shinned hawks (Accipiter striatus) were the most commonly observed species. A total of 232 birds, 33 percent of all observations, occurred in the Project area below the maximum rotor-swept zone of the proposed turbines.


Four bald eagles (Haliaeetus leucocephalus) were observed during spring 2009 raptor surveys at the Project, two of which were within the Project area. The bald eagle is designated as a threatened species in New Hampshire. In addition, six osprey, a New Hampshire Species of Special Concern, were observed during spring raptor surveys. All but one of these birds was within the project boundary. There were five observations of three individual bald eagles over Tenney Mountain during the fall survey. One northern harrier (Circus cyaneus) was observed outside the Project area. Two state species of special concern, osprey (Pandion haliaetus) and American kestrel (Falco sparverius), were also seen in the Project area during the fall raptor survey.


Acoustic Bat Survey


The objectives of acoustic surveys were to document bat activity patterns and general species composition from August through October across the Project area, and to document bat activity patterns in relation to weather factors such as wind speed and temperature. Eight Anabat SD1 detectors (Titley Electronics Pty Ltd.) were deployed from August 11 to October 22 from 7:00 pm to 7:00 am for a total of 466 detector nights during the fall 2009 survey. Acoustic survey sites at Groton Wind Project were chosen based discussions with bat expert, Ed Arnett of Bat Conservation International (BCI) as well as Stantec? experience conducting these types of surveys. In order to document how bats might move across the Project area, acoustic bat detectors were deployed along each of the three ridgelines in the Project area proposed for wind turbines. Two detectors were deployed 15 meters high in portable towers on the southern end of the Fletcher Mountain ridgeline and the small subsidiary ridge to the north. Three detectors were deployed at the met tower in the middle of Tenney Ridge and three detectors were deployed at the met tower at the north end of Tenney Ridge. The intent of the acoustic surveys was to (1) document bat activity patterns and general species composition from April through October; and (2) document bat activity patterns in relation to weather factors including wind speed, temperature, and relative humidity. Recorded call files were analyzed to species guild and tallied by night.


Between August 11 and October 22, a total of 2,104 call files were recorded by the eight detectors, resulting in an overall detection rate of 4.5 calls per detector-night. Call sequences belonging to all five guilds were identified during the acoustic survey. Migratory species of the big brown-silver haired guild composed the greatest percentage of all calls recorded during the fall 2009 survey period (45.5%). The Tenney Middle met tower detector (22 m) recorded the most calls (38%, n=802) during the fall season. Approximately 84 percent of all calls were recorded during the month of August, when detection rates peaked for all detectors. Species composition varied across acoustic detector height. There was no strong correlation between wind speed and detection rates, although there was a weak correlation between bat activity and mean nightly temperature.

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