RAPTOR RESEARCH STUDIES AT BLOCK ISLAND, RHODE ISLAND.

Transcription

1 2015 RAPTOR RESEARCH STUDIES AT BLOCK ISLAND, RHODE ISLAND. Biodiversity Research Institute Page 1

2 RAPTOR RESEARCH STUDIES AT BLOCK ISLAND, RHODE ISLAND. WILDLIFE SCIENCE CHANGING OUR WORLD SUBMITTED TO: Scott Comings The Nature Conservancy P.O. Box High Street Block Island, RI And The Bailey Wildlife Foundation Cambridge, MA SUBMITTED BY: Chris DeSorbo Director, Raptor Program Biodiversity Research Institute 276 Canco Rd Portland, ME SUBMITTED ON: October 7, 2015 Biodiversity Research Institute Page 2

3 Biodiversity Research Institute (BRI) is a 501(c)(3) non-profit organization located in Portland, Maine. Founded in 1998, BRI's mission is to assess emerging threats to wildlife and ecosystems through collaborative research, and to use scientific findings to advance environmental awareness and inform decision makers. To obtain copies of this report contact: Biodiversity Research Institute 276 Canco Road Portland, ME USA (207) chris.desorbo@briloon.org FRONT PHOTO: Perched Peregrine Falcon following release from sampling and transmitter fitting at the Block Island Raptor Research Station. Photo credit: Rick Gray SUGGESTED CITATION: C. R. DeSorbo, R. B. Gray, C. Persico, and D. Riordan. Raptor Research Studies at Block Island, Rhode Island, BRI Report # submitted to The Nature Conservancy, Block Island, Rhode Island, and The Bailey Wildlife Foundation, Cambridge, Massachusetts. Biodiversity Research Institute, Portland, Maine. 39 pp. Biodiversity Research Institute Page 3

4 Table of Contents LIST OF FIGURES EXECUTIVE SUMMARY INTRODUCTION STUDY AREA OBJECTIVES METHODS Research Station Establishment Raptor Banding and Sampling Instrumenting Raptors with Transmitters RESULTS AND DISCUSSION Timing, Intensity and Species Composition Migratory Connectivity: Migration Routes, Wintering Areas, Origins Evaluating Mercury Exposure in Migrant Raptors using the Atlantic Flyway Evaluating the Suitability of the Block Island Raptor Research Station for long-term Raptor Research LITERATURE CITED Biodiversity Research Institute Page 4

5 LIST OF FIGURES Figure 1. Removing a Peregrine Falcon from a dho gaza net Figure 2. Banding a raptor using a lock-on band (left), and measuring the culmen of a juvenile Sharp-shinned Hawk Figure 3. Measuring wing cord (left) and tail length of Peregrine Falcons at the Block Island Raptor Research Station Figure 4. Example of 12g solar and 22g solar GPS satellite transmitters used to track migratory movements of Peregrine Falcons (left); a hooded Merlin being fitted with a transmitter (right) Figure 5. Female HY Merlin fitted with a 5g satellite transmitter (left), male HY Peregrine Falcon (right) fitted with a 12g solar satellite transmitter at the Block Island Raptor Research Station Figure 6. Hatching year male Northern Harrier fitted with a 6g solar satellite transmitter at the Block Island Raptor Research Station Figure 7. Location of automated radio telemetry towers in the Mid-Atlantic U.S. during 2014 deployment of transmitters on Merlins on Block Island Figure 8. Female HY Merlin harnessed with backpack-mounted digitally coded VHF transmitter, or 'nanotag' Figure 9. Total number of diurnal raptors trapped by species and year at the Block Island Raptor Research Station, Figure 10. Annual species composition of diurnal raptors captured at the Block Island Raptor Research Station Figure 11. Number of Peregrine Falcons captured by date, Figure 12. Number of Merlins captured by date, Figure 13. Fall migration routes of 6 male Peregrine Falcons instrumented with satellite transmitters on Block Island, RI, Figure 14. Fall migration routes of nine female Peregrine Falcons (1 adult, 8 HYs) instrumented with satellite transmitters on Block Island, RI ( ) and Monhegan Island, ME (2010) Figure 15. Fall migratory movement of Peregrine Falcon HYM02 after departure from Block Island Raptor Research Station, as indicated by satellite telemetry Figure 16. Peregrine HYF02 photographed in The Bahamas, following instrumentation with a satellite transmitter in fall 2012 at the Block Island Raptor Research Station Figure 17. Five spring migration routes of four female Peregrine Falcons tracked using satellite telemetry Figure 18. Spring migration route of Peregrine Falcon ADF02, fitted with a satellite transmitter on Block Island, fall Figure 19. Fall migration paths of two HY female and one adult female Merlin, tracked from Block Island, RI using satellite telemetry Figure 20. Fall and spring migration paths of an adult female Merlin tracked from Block Island, RI using satellite telemetry Figure 21. Detection histories of 18 Merlins fitted with digitally coded VHF transmitters (nanotags) on Block Island, Rhode Island Biodiversity Research Institute Page 5

6 Figure 22. Distribution of flight duration for 18 Merlins travelling between (last detection) Block Island, Rhode Island, or Montauk, New York to (first detection) southern Virginia Figure 23. Fall movements of a hatching year male Northern Harrier tracked from Block Island, RI, using satellite telemetry Figure 24. Feather Mercury concentrations in eight species of migrant raptors sampled at the Block Island Raptor Research Station Figure 25. TNC and BRI hosting a school group at the Block Island Raptor Research Station. TNC s Scott Comings showcases a hatching year Peregrine Falcon during the James Stover Series nature walk Figure 26. Educational outreach efforts by TNC and BRI. BRI s Chris Persico displays poster showing migration routes of Peregrine Falcons tracked from Block Island using satellite telemetry during the James Stover Series nature walk Biodiversity Research Institute Page 6

7 1.0 EXECUTIVE SUMMARY During fall seasons of , we established the Block Island Raptor Research Station on Block Island, Rhode Island to facilitate several research investigations on migratory raptors. This is the first effort to study migrant raptors on Block Island. This raptor research station is likely the farthest north and farthest offshore compared to others along the Atlantic migration flyway. The objectives of this study were to: (1) characterize the timing, intensity, and species composition of the raptor migration at Block Island, (2) determine migration routes, overwintering locations and presumed origins of migrant raptors using Block Island during migration and (3) establish baseline mercury exposure levels in migrant raptors and make species comparisons. Lastly, we consider based on current findings the value and efficacy and of establishing a long-term Raptor Research Station on Block Island. 1. We captured 472 individuals of eight different raptor species on Block Island during fall seasons. Roughly three-quarters of raptors captured annually and overall were falcons. In general, Merlins comprised roughly one-half of annual captures, while Peregrine Falcons (peregrine hereafter) comprised one-quarter of captures. Sharpshinned Hawks, Cooper s Hawks, Northern Harriers, American Kestrels, Red-tailed Hawks, and Northern Goshawks generally comprised the remaining quarter of annual captures. A notable increase in peregrine captures marked the 2014 season such that peregrines approached nearly half of all individuals captured during that year. The vast majority of raptors captured on Block Island were of the hatching year age class. 2. Captures on Block Island generally reflected typical migration timing for peregrines and Merlins, with the bulk of the peregrine captures occurring during the first 7-10 days of October. The Merlin migration on Block Island was more protracted compared to peregrines, with the annual peak ranging from 23 September to 1 October. 3. We fitted 14 peregrines with satellite transmitters on Block Island to learn about migration routes, wintering areas, and presumed origins. Combined with two peregrines tracked from Monhegan Island, Maine, these peregrines have generated one of the most extensive datasets available on peregrine migration in the Atlantic flyway. Peregrines wintered extensively in the Caribbean and Central and South America. Preliminary data suggested male peregrines may migrate further than females, but larger sample sizes are needed. 4. Five satellite-tracked peregrines (six tracks) provided information on spring migration routes and presumed/possible origins. Potential origins spanned from central Saskatchewan to Greenland. Satellite-tracked peregrines generally used little of the Atlantic Flyway during northward migration. Four peregrines travelled through the center of the U.S. west of the Great Lakes, one travelled north from the mid-atlantic U.S., and one individual migrated through eastern Quebec and Nunavut to Greenland after overwintering on Block Island. 5. This study is the first in which Merlins have been tracked using satellite telemetry or automated telemetry (i.e., nanotags ). Three satellite-tagged Merlins provided Biodiversity Research Institute Page 7

8 information on fall migration routes to Florida; one overwintered in Puerto Rico. One Merlin provided information on spring migration routes and is presumed to have originated from eastern Quebec or possibly Labrador. We fitted 39 Merlins with nanotags to learn about movements along the Atlantic coast, pace of migration, and stopover behavior. Of tagged Merlins, 38% were detected at 1 tower. Merlins were detected at towers in MA (Cape Cod), CT and along the Atlantic coastline to the south of Block Island, particularly in NJ and VA. Lacking detections for 18 individuals was suggestive of offshore habitat use, which is consistent with findings of satellite telemetry. The majority of migrating Merlins travelled between Block Island/Montauk and Virginia in roughly five days. 6. In a pilot effort, we fitted one Northern Harrier with a satellite transmitter. Counter to expectations, this hatching year male migrated north to Connecticut prior to spending nearly six weeks north of Buzzard s Bay in the Cape Cod region of MA. 7. We evaluated mercury (Hg) exposure in eight species of raptors captured on Block Island. Patterns of Hg exposure in species were generally similar in blood and feather indices. Feather Hg concentrations were highest in Sharp-shinned Hawks, peregrines and Merlins. American Kestrels may have similar feather Hg concentrations to Merlins, but sample sizes preclude powerful comparisons. Adverse effect thresholds for Hg are not well-established for species sampled in this study; however some individuals exceeded levels associated with reproductive effects in other species. 8. The Block Island Raptor Research Station provided exceptional opportunities for conducting environmental education and outreach programs. During seasons, BRI and TNC partnered to conduct educational outreach programs focusing on ecology, raptors, migration, contaminants, and environmental issues. Target audiences were of all ages and included school groups, the general public, conservation professionals, ecotourism groups, figures, and high level government decision-makers. 9. Our efforts on Block Island indicated the Block Island Raptor Research Station is uniquely suited to fill data gaps important to numerous conservation and management issues. The location of the station in the northern portion of the U.S. Atlantic Flyway (compared to numerous such stations in the mid-atlantic U.S. for example) is important because birds captured at northern latitudes provide information on habitat use along the largest portion of the Atlantic Flyway possible. Such information has become important in efforts to understand exposure risk of migrant raptors such as peregrines and others relative to proposed offshore wind energy areas in the mid-atlantic U.S. and elsewhere along the U.S. coast. Biodiversity Research Institute Page 8

9 2.0 INTRODUCTION Migratory birds, particularly songbirds, shorebirds, and raptors, travel thousands of miles twice a year between breeding areas and wintering areas. Some birds travel en masse in spectacular migration events, while others travel inconspicuously alone. Many bird species use relatively well-documented continental-scale migration corridors, or flyways, to travel between breeding and wintering areas. The Atlantic Flyway along the Atlantic coast of the U.S. represents a major migratory throughway for tens of thousands of birds originating from throughout much of eastern and central North America or elsewhere. Even species originating from Greenland, such as tundrius Peregrine Falcons, cross the Atlantic at high latitudes and use the Atlantic Flyway to reach wintering areas in Central and South America. Information documenting the migratory habits of birds is important in developing effective conservation strategies. Conservation biologists recognize that many bird populations face threats in their breeding areas, their wintering areas, and during migration. Effective conservation measures for migratory species protect individual populations at each stage of their annual life cycle. In many species, links between populations in breeding areas and wintering areas remain poorly established, and important stopover habitats used to rest and refuel during migration are poorly documented. These notable data gaps stem from significant challenges in collecting information about birds that travel vast distances in remote areas annually. Notable developments in animal tracking technologies are rapidly advancing our understanding of the migratory ecology of birds. While traditional research approaches relied upon banding and opportunistic band encounters that occurred infrequently (i.e., 1-3% of birds banded were encountered), tracking technologies now offer the possibility of documenting daily even hourly movement patterns of individual birds continuously over time. Individual animal tracking data is increasingly being used by conservation biologists and regulators to fill-in substantial data gaps in our understanding of species needed to inform management and conservation decisions. Animal tracking data is routinely used to map migration routes, identify wintering and stopover habitats, and to inform wildlife risk assessments. The ability to use tracking data toward multiple and widely differing conservation and research applications often justifies the high cost of some types of transmitters. In 2009, BRI began searching for a suitable site from which migrant raptors using the Atlantic Flyway could be captured and studied to aid in migration studies, contaminant exposure assessments, and offshore wind energy risk assessments. Relatively few sites exist in which raptors using coastal migration routes can be captured efficiently along the Atlantic coast. Valuable sites exist in Mid-Atlantic states and southward (i.e., Cape May, NJ, Assateague Island, MD/VA, Kiptopeke, VA, Florida Keys); however, few opportunities exist to efficiently capture migrating raptors using the Atlantic flyway north of Cape May, NJ. Over the last decade, the need for a raptor research station north of the Mid-Atlantic U.S. states has become evident as offshore wind energy facilities are being built or proposed in both state (< 3 nautical mi from shore) and federal (>3 nautical mi from shore) waters throughout the Atlantic Flyway (BOEM Biodiversity Research Institute Page 9

10 2015), and the risks these facilities pose to migrating birds (particularly raptors) remains poorly understood. Research stations located in the northern portion of the U.S. Atlantic flyway are optimal for research purposes, because they enable researchers to capture raptors before they encounter wind energy facilities or other research stations to the south. Raptors are a primary bird group associated with collision risks at terrestrial-based wind energy projects; however, they are generally overlooked compared to waterbirds in offshore settings. Peregrine Falcons, Merlins, and several other species capable of enduring lengthy over-water flight are commonly encountered offshore. With an increasing number of offshore wind energy facilities being proposed along the Atlantic flyway, further evaluations of the degree to which migrating raptors might encounter or collide with offshore wind energy facilities are warranted. In 2012, BRI established the first raptor research station on Block Island, RI the Block Island Raptor Research Station. Block Island is well-known in the recreational birding community for its spectacular songbird migration, but no one had previously attempted to use it to study migrant raptors. The location of Block Island was strategically attractive because it was situated north of a large number of proposed offshore wind energy areas, as well as other research stations that could encounter released migrants as they continue their southward migration. Field efforts in were funded in part by a grant from the Department of Energy, due to the inclusion of Peregrine Falcons in BRI s Mid-Atlantic baseline study, which aims to collect information on wildlife densities, distribution patterns and movements along the Mid-Atlantic U.S. (Williams et al. 2015). Such information is needed to inform siting, permitting and mitigation efforts for potential future wind energy development areas offshore from Delaware, Maryland and Virginia. BRI s efforts in 2012 revealed not only that the Block Island Raptor Research Station was an optimal location in which migrating Peregrine Falcons could be studied, but that it also offered opportunities to learn about other raptor species such as Merlins, Northern Harriers, and others. In , we fitted 12 Peregrine Falcons (peregrine hereafter) with satellite transmitters on Block Island. While data from these peregrines (and two deployed by BRI in 2010) substantially increased our understanding of peregrine movements in the Atlantic flyway, a higher sample size remained needed to enable robust movement modelling analyses. Furthermore, similar information does not exist for several other species, such as Merlins, Northern Harriers, American Kestrels, and others. In 2014, BRI partnered with The Nature Conservancy (TNC) and researchers at the University of Rhode Island to strategize how to continue operation of the Block Island Raptor Research Station. With a grant from The Bailey Wildlife Foundation, and support from TNC, the Ocean View Foundation, the Bluestone Foundation, BRI was able to continue operation of the Block Island Raptor Research Station in We fit more peregrines with satellite transmitters in 2014, expanded tracking efforts to include Merlins and Northern Harriers, and intensified sampling efforts to evaluate the exposure of migrant raptors to mercury and other contaminants. In collaboration with researchers at the University of Rhode Island, we fitted 39 Merlins with digitally coded VHF tags (often referred to as nanotags ) to learn about migratory and stopover habits of Merlins. With continuing support from our partners, BRI is continuing the operation of the Block Island Raptor Research Station again in In collaboration with Biodiversity Research Institute Page 10

11 TNC, we will increase our educational outreach efforts in 2015 and will further evaluate its relevance to the raptor research community and conservation. Findings from BRI s study evaluating the exposure and risks of offshore wind energy facilities in the Mid-Atlantic U.S. to peregrines (DeSorbo et al. 2015) is to be publically released by early October (see Here, we summarize efforts and preliminary findings from various aspects of our research at the Block Island Raptor Research Station on Block Island during , and evaluate the efficacy and value of continuing raptor research investigations from this station. 3.0 STUDY AREA Block Island is located 13 miles (21 km) south of Point Judith, Rhode Island and 14 miles (23 km) due east from Montauk, NY. The island is approximately 9.7 square miles (52.2 km²). Roughly 40 percent of the island is protected from development. The northern three-quarters of coastline consist of sand dunes and beaches broken up by low clay-based cliffs. Coastlines in the southern portion of the island are characterized by high clay-based cliffs and extensive sand beaches. The Block Island Raptor Research Station is situated on private conservation land in the southwest corner of Block Island. The banding station was surrounded from the south and west by pasture land sectioned by hedgerows, and to the north and east small open spaces are interspersed with groups of conifers. 4.0 OBJECTIVES 1. Characterize the timing, intensity, and species composition of the raptor migration at Block Island. 2. Migratory connectivity: determine migration routes, overwintering locations and presumed origins of for migrant raptors using BI during migration. 3. Establish baseline Hg exposure levels in BI s migrant raptors and make species comparisons. 4. Evaluate the efficacy and value of establishing a long-term Raptor Research Station on Block Island. 5.0 METHODS 5.1 Research Station Establishment In fall 2011, BRI explored Block Island to find a location suitable for establishing a raptor research station. Many factors were considered, including property ownership, public use, habitat type, topography, and location relative to the presumed flightpath of fall migrant raptors. With these considerations in mind, we selected a privately owned property in the southwestern portion of Block Island. The station was generally modeled after similar well- Biodiversity Research Institute Page 11

12 established stations elsewhere (i.e, Cape May, NJ, Monhegan Island, BRI; DeSorbo et al. 2012) which rely upon using lures to attract raptors to the station and then capturing them using a combination of bow nets, mist nets and dho gaza nets (Figure 1). Figure 1. Removing a Peregrine Falcon from a dho gaza net. 5.2 Raptor Banding and Sampling Upon capture, we removed raptors from traps, banded them using U.S. Geological Survey (USGS) leg bands, and collected standard morphometric data (flat wing cord, tail, culmen, body mass) following standard protocols (Figure 1, Figure 2, Figure 3). Each bird was given a rudimentary health evaluation which included classifying both the crop and breast muscle mass into four size classes (0-3). All birds were visually inspected for abnormalities or injuries. We plucked 2-3 feathers from the rump and breast of all individuals. Feathers are used for analyses of mercury (Hg), and will be further considered for analyses of other metals, stable isotopes, genetics, and sample archives. We collected blood samples from a portion of captured individuals following standard protocols (Fair et al. 2010). Many birds were photo-documented. Figure 2. Banding a raptor using a lock-on band (left), and measuring the culmen of a juvenile Sharp-shinned Hawk. Biodiversity Research Institute Page 12

13 Figure 3. Measuring wing cord (left) and tail length of Peregrine Falcons at the Block Island Raptor Research Station. 5.3 Instrumenting Raptors with Transmitters Satellite Transmitters Satellite telemetry has revolutionized the our understanding of animal movements because it provided a means of tracking movements of animals travelling vast distances and in remote regions that were otherwise impossible or impractical (Seegar et al. 1996). Transmitters attached to individuals can fix both GPS and Doppler or Argos locations (with varying degrees of accuracy), which can be received by globally orbiting satellites and relayed to users. GPS locations are generally associated with higher levels of accuracy compared to Argos locations (Douglas et al. 2012). We attached satellite transmitters (Platform Transmitter Terminals, or PTTs) to a subset of captured raptors, prioritizing peregrines that were visibly healthy and heavier, such that the PTT package remained 3.5% of bird body mass. Transmitters were instrumented to individuals with backpack-style harnesses made of 0.25 in (6.35 mm; peregrine) or in (4.76 mm; Merlin) Teflon ribbon (Bally Ribbon Mills, Bally, PA) sewn with Teflon thread through a Teflon kangaroo leather patch centered on the breast (Kenward 2001, Steenhof et al. 2006, Walls and Kenward 2007, Fair et al. 2010) (Figure 4). Satellite transmitters fixed both GPS and Doppler (or Argos ) locations. The location error for GPS locations typically ranges from 5 15m. Argos locations are classified into 7 different location classes by CLS America according to their associated error (Douglas et al. 2012, CLS 2015). Implausible locations were removed from our location dataset using the Douglas Argos Filter (DAF) (Douglas et al. 2012). Biodiversity Research Institute Page 13

14 Figure 4. Example of 12g solar and 22g solar GPS satellite transmitters used to track migratory movements of Peregrine Falcons (left); a hooded Merlin being fitted with a transmitter (right). We fitted individuals of the following three species with PTTs as follows during at the Block Island Raptor Research Station: Peregrines: We fitted 14 satellite transmitters to peregrines captured on Block Island (Figure 5). Included in summaries here also are two hatching year (HY hereafter) females fitted with transmitters on Monhegan Island in 2010 (DeSorbo et al. 2012). Thus, data from 16 instrumented peregrines were available for analysis. Of these individuals, two were adult females, six were HY males, and eight were HY females. Merlins: We fitted four satellite transmitters to Merlins on Block Island in 2014 (Figure 5). All transmitters were 5 g units, fit to one adult female and three HY females. Northern Harrier: In a pilot effort, we fitted one 6g satellite transmitter to a HY male Northern Harrier in 2014 (Figure 6). Figure 5. Female HY Merlin fitted with a 5g satellite transmitter (left), male HY Peregrine Falcon (right) fitted with a 12g solar satellite transmitter at the Block Island Raptor Research Station. Biodiversity Research Institute Page 14

15 Figure 6. Hatching year male Northern Harrier fitted with a 6g solar satellite transmitter at the Block Island Raptor Research Station Automated Radio Telemetry ( nanotags ) In 2014, we collaborated with researchers at the University of Rhode Island to fit 39 Merlins (20 females, 19 males) with digitally-coded telemetry tags (commonly referred to as nanotags; manufactured by Lotek Wireless, Newmarket, Ontario, Canada) in order to gain perspectives on Merlin migration along the Atlantic coast. Nanotags emit individual-specific VHF signals that can be detected at automated telemetry receiving towers erected by network research partners. A network of coordinated automated telemetry receiving towers (the MOTUS wildlife tracking system, see is growing rapidly in North America, particularly along the Atlantic coast (Figure 7). This tracking system enables researchers to economically gather information on wildlife movement patterns and stopover behavior at a large geographic scale, providing individuals fly within the detection range of towers (detection range ranges up to 15 km, but varies widely according to many factors including transmitter type, topography, weather conditions, etc.). Figure 7. Location of automated radio telemetry towers in the Mid-Atlantic U.S. during 2014 deployment of transmitters on Merlins on Block Island. Biodiversity Research Institute Page 15

16 *White arrow indicates deployment site, Block Island, RI. Colored pins indicate automated telemetry towers with six (green), three (orange), and two (blue) antennas. Figure courtesy of Adam Smith, URI. Figure 8. Female HY Merlin harnessed with backpack-mounted digitally coded VHF transmitter, or 'nanotag'. Males were fitted with both tailmount and backpack transmitters; females were fitted with backpacks only to achieve greater unit lifespan (Figure 8). After harnessing, male backpacks weighed approximately 2.5 g, and female backpacks weighed approximately 4.5 g. Tailmount units fitted to males weighed approximately 1.6 g at deployment. Transmitter lifespan is estimated by the manufacturer to be approximately 84 d and 459 days for male and female units, respectively. 6.0 RESULTS AND DISCUSSION 6.1 Timing, Intensity and Species Composition We captured a total of 472 individual diurnal raptors 1 during fall capture efforts during Eight species were represented in captures. Annually, we captured 141 raptors in 2012, 121 in 2013, and 210 in Lower trapping numbers in 2013 were considered to be largely related to multiple days of eastern and southern winds typically considered to lessen the number of migrant birds reaching Block Island. Higher capture totals in 2014 reflect an increase in the number of peregrines trapped compared to 2012 and 2013 seasons. We suspect increased peregrine captures were influenced at least in large part by: (a) winds favoring peregrine migration to Block Island (northwest winds), immediately followed by winds that deterred their departure (south winds), and (b) favorable reproduction in breeding areas. Higher peregrine trapping counts were detected at other trapping stations along the Atlantic coast such as on Assateague Island, MD (M. Yates, Earthspan Inc., pers. comm.). 1 In 2014, two individuals were recaptured a few days after initial capture and a third individual was captured twice more after initial capture, hence total captures were 476. Biodiversity Research Institute Page 16

17 Figure 9. Total number of diurnal raptors trapped by species and year at the Block Island Raptor Research Station, *Species codes follow American Ornithologist Union convention: Northern Goshawk (NOGO), Red-tailed Hawk (RTHA), American Kestrel (AMKE), Cooper s Hawk (COHA), Sharp-shinned Hawk (SSHA), Northern Harrier (NOHA), Peregrine Falcon (PEFA) and Merlin (MERL). Merlins (59-87 captured annually) generally comprised about one half of all individuals captured each year (Figure 9, Figure 10). Peregrines (25-91 captured annually) comprised 21 25% of all captures during 2012 and 2013; however, peregrines comprised 43% of all captures during Northern Harriers (n = 9-16) and Sharp-shinned Hawks (n = 7-14) each comprised 7% of all individuals captured annually. Cooper s hawks (n = 7-8) comprised 5% of all individuals captured annually. American Kestrels (n = 0-5) were captured in 2012 and 2014; however, none were captured in One Northern Goshawk and one Red-tailed Hawk were captured in 2012; neither species has been captured since. Biodiversity Research Institute Page 17

18 Figure 10. Annual species composition of diurnal raptors captured at the Block Island Raptor Research Station. NOGO = Northern Goshawk, RTHA=Red-tailed Hawk, AMKE = American Kestrel, COHA = Cooper s Hawk, SSHA = Sharp-shinned Hawk, NOHA = Northern Harrier, PEFA = Peregrine Falcon, MERL = Merlin. Age Class Summary The vast majority (97.5%) of all raptors captured on Block Island were young of the year (hatching year; HY hereafter). We captured adults in three of the eight species in the study; four peregrines (2.6% of all peregrines trapped), six Merlins (2.7%), and two Northern Harriers (5.7%). Timing Distinct timing patterns were evident for some, but not all species of raptors. Sample sizes of some species were limited for evaluating migration timing for some species. Peregrines were trapped from September to October during seasons (Figure 11). The peak day of peregrine captures occurred between 6 8 October during seasons. Individuals captured on these three days accounted for 41% of all peregrines captured during Merlins were captured from September to October. Merlin captures were generally more evenly distributed over the course of the trapping season, reaching a peak between 23 September and 1 October (Figure 12). Individuals captured over this span (9 d) Biodiversity Research Institute Page 18

19 accounted for 42% of all Merlins trapped during Migration timing of other species was difficult to evaluate due to lower sample sizes over the period. Figure 11. Number of Peregrine Falcons captured by date, Figure 12. Number of Merlins captured by date, Daily capture total data provided useful perspectives on migration timing for some commonly captured species at Block Island, RI such as peregrines and Merlins. Daily capture data shows a general consistency in the peak timing for peregrine migration generally within the first 7-9 days of October during seasons (Figure 11). Biodiversity Research Institute Page 19

20 The timing of the Merlin flight, as indicated by capture data, was notably more consistent at low numbers and seasonally protracted in comparison to peregrines (Figure 12). The timing of captures of other raptor species was highly variable; sample sizes for other raptors species preclude powerful conclusions about migration timing on Block Island or the region. Typically, migration count data, rather than daily capture data such as used here, is more accurate in characterizing the timing and intensity of raptors passing through an area during migration. The Hawk Migration Association of North America (HMANA) provides regularly updated annual hawk count information for over 275 North American hawk watch sites ( Site-specific migration information on this website can be of value to the general public and researchers in placing local migration patterns in a broader regional context. In general, migration timing patterns for raptors captured on Block Island were consistent with general knowledge of migration timing for each species; however, migration count data from other offshore sites are rare to enable comparisons. Limited annual capture totals for some species, such as the Accipiter hawks (Sharp-shinned Hawks, Cooper s Hawks) and American Kestrels on Block Island preclude use of this data in characterizing local migration patterns. Since support for field efforts in this project were specifically linked to capture efforts (i.e., capturing individuals and fitting them with transmitters, sampling), staffing has been insufficient to support a standardized count on Block Island independent from trapping operations. Raptor migration counts on island stopovers can be complicated compared to counts at mainland sites because birds regularly remain at island stopovers for variable amounts of time, and care must be taken to avoid double-counting individuals by only counting individuals confirmed to be departing from (or arriving on) the island (DeSorbo et al. 2012). Attempts during 2012 and 2013 seasons to use our trapping lookout used to detect and relay location of local raptors to trappers were insufficient for use in gathering reliable raptor migration counts due to regular local foraging activity and few departure confirmations. Efforts to learn about raptor migration at Block Island using standardized counts could improve our understanding of general migration patterns. For example, understanding arrival and departure directions for migrant raptors at Block Island has a variety of management and conservation implications, such as evaluating potential risks posed by wind turbines or other facilities constructed on the island or offshore. At present, automated radiotelemetry (Merlins, see section 6.2) and to a lesser degree, satellite telemetry (section 6.1) are the two primary means of collecting such information on Block Island. 6.2 Migratory Connectivity: Migration Routes, Wintering Areas, Origins Peregrine Falcons Wintering Areas The datasets of the 14 peregrines fitted with satellite transmitters on Block Island, combined with the two individuals fitted with transmitters on Monhegan Island, may comprise the most substantial information to date on peregrine movement patterns along the Atlantic Flyway. This Biodiversity Research Institute Page 20

21 dataset is especially unique in that HY peregrines have rarely been previously tracked using satellite telemetry (likely due to the cost of satellite units and high anticipated annual mortality of HY peregrines). Fall migrant peregrines overwintered in locations across a wide geographic range, spanning throughout the Bahamas, Central America, and South America (Figure 13, Figure 14). Preliminary patterns based on limited sample sizes suggest a tendency for males to travel further than females to reach overwintering areas. For example, while the majority of females (7 of 9 individuals) overwintered in the Bahamas and Cuba (Figure 14), four of the six instrumented males travelled to Central and South America (Columbia, Costa Rica, Venezuela, and San Andres Island, a Columbian-owned island ~ 250 km off the east coast of Nicaragua) (Figure 13). Two males did not complete fall migrations. One travelled due east after release on an impressive and unique transoceanic journey 1500 km into the Atlantic (Figure 15). Speeds travelled by this individual during individual days and its prolonged time offshore are highly suggestive that this individual was resting and foraging from offshore vessels (Figure 15). One male peregrine did not complete its fall migration prior to mortality; it was recovered on Assateague Island, VA at the base of an eagle nest. Biodiversity Research Institute Page 21

22 Figure 13. Fall migration routes of 6 male Peregrine Falcons instrumented with satellite transmitters on Block Island, RI, Biodiversity Research Institute Page 22

23 Figure 14. Fall migration routes of nine female Peregrine Falcons (1 adult, 8 HYs) instrumented with satellite transmitters on Block Island, RI ( ) and Monhegan Island, ME (2010). Biodiversity Research Institute Page 23

24 Figure 15. Fall migratory movement of Peregrine Falcon HYM02 after departure from Block Island Raptor Research Station, as indicated by satellite telemetry. * Speeds presented in figure measured between first and last location of daily clusters of locations. Of the 10 female peregrines fitted with satellite transmitters, 9 migrated southward following release (Figure 14). The single individual that did not migrate following capture (ADF02) remained on Block Island for the winter (this case is discussed in the next section). Satellite data these nine peregrines overwintered in Turks & Caicos, The Bahamas, Cuba, the Dominican Republic, Jamaica, and Honduras. Peregrine Falcons presumed migration or natal origins Five peregrines provided insights into potential natal or breeding origins. Natal or breeding origins spanned across an expansive geographic area spanning from Manitoba, Canada east to Greenland (Figure 17, Figure 18). Presumed breeding areas or natal origins, from east to west, are summarized by individual below: ADF01 migrated through the southeastern and central U.S. to an area outside of Winnipeg in southern Manitoba, Canada in 2013 after overwintering in Jamaica. Final transmissions for this female were in an agricultural field, interestingly, very close to the location in which a peregrine from a Canadian study was recovered. Search efforts conducted by colleagues were successful in recovering the transmitter, some remains, and the band; however, causes of mortality remain unknown. After overwintering the winter of on the Turks and Caicos Islands, HYF07 migrated through the southeastern and central U.S. to a small lake in an agricultural area outside Saskatoon in south-central Saskatchewan, Canada in spring After returning to the same wintering grounds in the winter of , this female Biodiversity Research Institute Page 24

25 migrated through the southeastern and central U.S. to the southwestern shores of the Hudson Bay before arriving in far northern Quebec, Canada on the eastern shore of the Hudson Bay in spring After overwintering in the Dominican Republic, HYF08 migrated across the Gulf of Mexico then travelled northward through the Great Plains of the central U.S. to an agricultural area outside of Regina in southeastern Saskatchewan in spring After overwintering in The Bahamas (Crooked Island; where she was photographed; Figure 16), HYF02 migrated northward along the Atlantic Coast of the U.S. to Cape May, NJ. She then travelled north over land through Quebec, Canada to northern Quebec near the Hudson Strait in spring ADF02 overwintered in the vicinity of Block Island during winter In the spring of 2014, she migrated northward over land to Quebec, then bisected the Labrador Peninsula en route to the Labrador Sea, before ultimately crossing the Davis Strait and departing the mainland from Cape Dyer (Nunavut, Canada) to Greenland (Figure 18). ADF02 spent the 2014 breeding season in Greenland but transmissions ceased in late September. ADF02 transmitted in mid-june 2015; but location data is suggestive of a mortality. Figure 16. Peregrine HYF02 photographed in The Bahamas, following instrumentation with a satellite transmitter in fall 2012 at the Block Island Raptor Research Station. Biodiversity Research Institute Page 25

26 Figure 17. Five spring migration routes of four female Peregrine Falcons tracked using satellite telemetry. Biodiversity Research Institute Page 26

27 Figure 18. Spring migration route of Peregrine Falcon ADF02, fitted with a satellite transmitter on Block Island, fall Biodiversity Research Institute Page 27

28 Merlins Migration Routes, Wintering Areas and Presumed Origins (satellite telemetry) We fitted four female Merlins, three HYs and one adult, with 5g satellite transmitters. These are the first Merlins to be tracked using satellite telemetry. Two of the HY Merlins and the adult migrated down the Atlantic U.S. coast to Florida (Figure 19). A fourth transmitter, fitted to a HY Merlin, did not provide useable data due to either mortality or unit failure. Of the three Merlins tracked down the Atlantic seaboard, two showed clear signs of use of offshore habitat, which should be considered in future efforts to evaluate the potential effects of offshore wind energy facilities on wildlife. Migration counts on Monhegan Island in Maine found that Merlins were the most commonly observed offshore migrant raptor. The two HY Merlins ceased transmitting in late October in Florida for unexplained reasons (i.e., mortality, unit failure, solar panel obstruction). Biodiversity Research Institute Page 28

29 Figure 19. Fall migration paths of two HY female and one adult female Merlin, tracked from Block Island, RI using satellite telemetry. The adult female (ADF01) continued migrating from Florida to Cuba, where it crossed over to the Dominican Republic, and then to Puerto Rico, where it spent the winter. Satellite communications ceased for much of the winter until the spring, at which point it retraced much of its southward migration path north to Petit-Mecatina, Quebec (Figure 20). This individual transmitted from this general location for approximately 20 days until transmissions ceased on 2 June Based on observed movement patterns, we speculate that this individual likely originated from eastern Quebec or Newfoundland/Labrador, possibly from the general region to which it migrated. This individual is likely the first Merlin for which a complete or nearcomplete migration track has been documented. Figure 20. Fall and spring migration paths of an adult female Merlin tracked from Block Island, RI using satellite telemetry. Biodiversity Research Institute Page 29

30 Merlins Migration Patterns Along the Atlantic Coast (Automated Radiotelemetry) Of the 39 nanotags fitted to Merlins, 92% (36 of 39) were detected by at least one tower along the Atlantic coast. Thirty-eight percent (14 of 36) of Merlins were only detected by towers on Block Island or nearby Montauk Island. Three Merlins were detected at towers on Cape Cod, MA, while one Merlin was detected at a tower in eastern Connecticut. Patterns of detection indicated that most Merlins leave Block Island to the south or southwest, although northwest or northeast departures are also possible. Of the 36 Merlins detected by at least one tower, 50% (18 of 36) were detected at towers in southern New Jersey and the Eastern Shore of Virginia NWR. Of these 18 Merlins, six were detected at receiving towers in southern New Jersey, and 16 (including four of those detected in New Jersey) were detected at Eastern Shore of Virginia NWR (Figure 21). Twelve Merlins departing Block Island avoided detection between Block Island or Montauk and Virginia, suggesting these Merlins used offshore habitats out of range of multiple tower arrays between Block Island and southern Virginia. In general, the majority of Merlins traveled between Rhode Island and southern Virginia in less than five days (Figure 22). Information on stopover patterns for migratory Merlins on Block Island are still being analyzed. This is the first study to track Merlins using automated telemetry. Regular detections of tagged Merlins enabled improved characterizations of Merlin migration along the Atlantic coast. Merlins commonly followed the Atlantic coastline, but lacking detections of individuals at some key receiving towers is suggestive of variable use of coastal and offshore habitats during migration. These findings are consistent with those indicated by satellite telemetry which verify use of offshore habitats by migrant Merlins. A relatively large sample size of tagged Merlins in this study enabled us to characterize different migratory strategies used by Merlins that are otherwise poorly documented by other approaches such as banding. Anticipated continual improvements in the network of automated telemetry receiving towers along the Atlantic coast and in wintering areas will strengthen our understanding of the migratory ecology of Merlins and other species in the future. The continued use of tracking technologies to learn about the migratory ecology of Merlins is warranted given generally low band encounter rates and large seasonal and locational biases in existing information and knowledge that Merlins may be the most abundant migrant raptor encountered in the offshore environment. Biodiversity Research Institute Page 30

31 Figure 21. Detection histories of 18 Merlins fitted with digitally coded VHF transmitters (nanotags) on Block Island, Rhode Island. *White numbers indicate number of tagged Merlins from Block Island detected in New Jersey (n = 6) and Virginia (n = 4; after detection in New Jersey; and n = 12 Block Island to Virginia). Arrows depict theoretical inshore/offshore migration routes based on detection histories for discussion purposes. Colored pins indicate automated telemetry towers with six (green), three (orange), and two (blue) antennas. Figure courtesy of Adam Smith, URI. Figure 22. Distribution of flight duration for 18 Merlins travelling between (last detection) Block Island, Rhode Island, or Montauk, New York to (first detection) southern Virginia. *Figure courtesy of Adam Smith, URI. Biodiversity Research Institute Page 31

32 Northern Harriers perspectives on migration We fitted one HY male Northern Harrier with a 6g PTT in Unlike virtually all other raptors fitted with satellite transmitters in this study, this male harrier did not appear to migrate southward in the fall. Northern Harrier HYM01 departed the island from the southwestern corner, travelled down a portion of Long Island, NY, until he headed northward through central Connecticut, where he spent roughly 5d before continuing on to Carver, MA just north of Buzzard s Bay (Figure 23). Northern Harrier HYM01 transmitted from the general vicinity of Carver, MA until its last transmission on 28 November, As is often the case in animal tracking studies, causes for ceased transmissions remain unclear. Movement patterns for HYM01 may reflect a tendency for Northern Harriers to overwinter in some southern New England States. The origin of Northern Harriers captured at Block Island during migration remains unknown. Figure 23. Fall movements of a hatching year male Northern Harrier tracked from Block Island, RI, using satellite telemetry. Biodiversity Research Institute Page 32

33 6.3 Evaluating Mercury Exposure in Migrant Raptors using the Atlantic Flyway. We evaluated mercury (Hg) exposure in eight species of diurnal migrant raptors captured at Block Island, RI during fall migration (Figure 24). Feather Hg concentrations differed significantly across the five species groups with a sample size of 12 (p <0.001, χ 2 = 30.12). Feather mercury concentrations were highly variable in almost all species. Merlins (mean ± SD: 2.2 ± 1.7 ug/g n = 132), peregrines (2.4 ± 1.7 ug/g, n = 60), and Sharp-shinned Hawks (2.5 ± 1.2 ug/g, n = 21) exhibited the highest feather Hg concentrations. Feather Hg concentrations in American Kestrels (1.9 ± 0.7 ug/g, n = 5) may be similar to Merlins, peregrines, and Sharp-shinned Hawks; however American Kestrel sample sizes are low and Hg concentrations were highly variable. The single Red-tailed Hawk (0.48 ug/g) and single Northern Goshawk (0.90 ug/g) captured and sampled contained the lowest feather Hg concentrations of all species sampled. Cooper s Hawks (1.2 ± 0.19 ug/g, n = 14) and Northern Harriers (1.2 ± 0.9 ug/g, n = 26) contained intermediate feather Hg concentrations relative to other species sampled. Figure 24. Feather Mercury concentrations in eight species of migrant raptors sampled at the Block Island Raptor Research Station. Species codes follow American Ornithologist Union convention: Red-tailed Hawk (RTHA), Northern Goshawk (NOGO), Cooper s Hawk (COHA), Northern Harrier (NOHA), American Kestrel (AMKE), Merlin (MERL), Peregrine Falcon (PEFA) and Sharp-shinned Hawk (SSHA). Blood Hg concentrations followed a somewhat similar pattern among species as that observed in feather Hg concentrations; however, blood Hg concentrations were highest in Merlins (0.84 ± 0.39, n = 31), followed by peregrines (0.79 ± 0.40, n = 14), and Sharp-shinned Hawks (0.62±0.22, n = 11 ug/g, n = 11). Northern Goshawks (0.30 ± 0.08 ug/g, n = 5) and Cooper s Hawks (0.42 ± 0.06 ug/g, n = 3) showed the lowest blood Hg concentrations among all species. Biodiversity Research Institute Page 33

34 Mercury in Migrant Raptors Mercury (Hg) pollution is a well-established environmental problem at a global scale. Mercury occurs naturally in our environment, but it is also produced through a wide variety of industrial activities. It can be deposited into ecosystems directly, or more commonly, through atmospheric deposition. Once deposited, Hg can be persistent in ecosystems and it readily accumulates in organisms. Bird tissues are commonly sampled and analyzed to gather insights on spatial and temporal patterns of Hg exposure, and to evaluate potential for adverse impacts. Blood reflects recent dietary exposure to Hg, and feathers can reflect a combination of recent dietary exposure and cumulated body burdens (Evers et al. 2005). Elevated Hg exposure is associated with a wide variety of adverse effects on animal behavior, reproduction, and physiology. Traditionally, toxicologists primarily considered Hg a risk for aquatic-based wildlife; however, recent studies have determined that Hg can also pose health risks to birds with nonpiscivorous diets, including those with diets comprised by terrestrial sources of protein such as passerines (Rimmer et al. 2005, Jackson et al. 2011) Recent studies have also further demonstrated that species vary widely in their sensitivity to mercury (Heinz et al. 2009). Efforts during this study have established baseline blood and feather Hg exposure concentrations in eight migrant raptor species. Sharp-shinned Hawks, Merlins, and peregrines had the highest exposure risk to Hg of the eight species sampled at the Block Island Raptor Research Station based on insights from blood and feather samples. Merlins had the highest blood Hg concentrations of all species, while Sharp-shinned Hawks had the highest feather Hg concentrations. American Kestrels may have Hg exposure levels in a similar range as Merlins, but sample sizes limit further insights. Blood and feather Hg concentrations associated with adverse effects have not been established for the raptors sampled in our study. Due to differences in Hg sensitivity among species, Hg adverse effect thresholds used for other well-established Hg bioindicator species such as Bald Eagles (Haliaeetus leucocephalus) Ospreys (Pandion haliaetus) (Bowerman et al. 1994, Anderson et al. 2008, Desorbo et al. 2009, Scheuhammer et al. 2012) and Common Loons (Evers et al. 2008) are likely inappropriate for use evaluating Hg impacts on migrant raptors captured on Block Island. Recent studies have documented, however, that forest songbirds and invertebrates are also exposed to Hg at levels higher than expected, and Hg exposure has been liked to adverse effects in some passerines (Jackson et al. 2011). For example, Jackson et al. (2011) found that blood and feather Hg concentrations of 0.7 ug/g and 2.4 ug/g respectively were associated with a 10% reduction in nest success in Carolina Wrens (Thryothorus ludovicaianus). In our study, individual Merlins, Sharp-shinned Hawks, peregrines, and American Kestrels exceeded one or both of these blood and feather Hg concentrations (Figure 24). Further study is needed to determine whether Hg levels associated with adverse effects in songbirds are relevant to raptors. Raptors with an evolutionary association with aquatic systems, such as peregrines and Merlins, may have a lower sensitivity to Hg effects compared to species associated with uplands and terrestrial ecosystems, such as Sharp-shinned Hawks. Significant population-level declines have been noted in several raptors species captured on Block Island, including Sharp-shinned Hawks, and American Kestrels (Viverette et al. 1996, Biodiversity Research Institute Page 34

35 Farmer et al. 2008, Smallwood et al. 2009), and further efforts to understand the exposure of populations to Hg or other threats are warranted in these species. 6.4 Evaluating the Suitability of the Block Island Raptor Research Station for longterm Raptor Research. Due to several different grants and the generous support of many parties (see acknowledgements), BRI has been able to operate a raptor research station on Block Island for the past three fall seasons ( ). This effort has enabled researchers to: 1. Build what is likely the most comprehensive dataset on peregrine and Merlin movements along the Atlantic flyway available. This dataset is valuable in efforts to: a. Link breeding and wintering locations for peregrines and Merlins using the Atlantic Flyway; b. Identify important migratory stopover habitat; c. Improve our limited understanding on the ecology of several raptor species needed to inform best conservation and management practices. 2. Evaluate potential exposure of peregrines to approved or proposed wind energy developments along the Atlantic Flyway. A report summarizing preliminary investigations to the potential exposure of peregrines to offshore wind energy areas in the Mid-Atlantic U.S. (among many other studies), is to be released by the Department of Energy and posted on BRI s website in October Evaluate mercury exposure in migrant raptors and evaluate potential for impacts; 4. Band raptors at a location strategically north of other raptor research/trapping stations along the Atlantic flyway; 5. Collect biological samples to: (a) be used toward analyses of genetics, other contaminants, or other investigations, and (b) to build a sample archive. The Block Island Raptor Research Station is unique in that it is likely the northernmost raptor research station along the Atlantic flyway. It is also probably the only such station on an offshore island, which has a large influence on the species composition of raptors observed. As a result, the Block Island Raptor Research Station is an ideal location for studying migrant falcons, particularly peregrines and Merlins. The location of the station in the northern portion of the U.S. Atlantic Flyway is important because birds captured at northern latitudes provide information on habitat use (i.e., stopover sites) along the largest portion of the Atlantic Flyway possible. The strategic location of Block Island for establishing a Raptor Research Station is highly pertinent to ongoing evaluations of the potential risks that wind energy facilities being proposed in state (< 3 nautical mi from shore) or federal waters (>3 nautical mi.) might pose to migrating raptors throughout the Atlantic Flyway. This station may also be useful in evaluating if raptors on Block Island are attracted to the wind energy facility currently being built off the coast of Block Island. Based on the notable amount of data amassed on raptors to date on Block Island during the seasons, it is clear that the Block Island Raptor Research Station is valuable to the research, conservation and education community. Biodiversity Research Institute Page 35

36 Education BRI and TNC have strived to use the opportunity of the Block Island Raptor Research Station to educate the general public about ecology, raptors, and important environmental issues (Figure 25, Figure 26). Over the past three years, BRI has hosted school groups, conservation members, and decision-makers such as Rhode Island s former Governor, Lincoln Chaffee, at the Block Island Raptor Research Station. In 2015, BRI and TNC have partnered to host formalized environmental education and outreach programs on Block Island to promote habitat and wildlife conservation and informed decision-making through field research. Over the next year, BRI and our project partners will explore options to enable the continuation of the Block Island Raptor Research Station for years into the future. Figure 25. TNC and BRI hosting a school group at the Block Island Raptor Research Station. TNC s Scott Comings showcases a hatching year Peregrine Falcon during the James Stover Series nature walk. Figure 26. Educational outreach efforts by TNC and BRI. BRI s Chris Persico displays poster showing migration routes of Peregrine Falcons tracked from Block Island using satellite telemetry during the James Stover Series nature walk. Biodiversity Research Institute Page 36