Appendix F: Birds

F.1 Introduction

This chapter of the RWSC Science Plan addresses bird research and associated scientific needs in the context of offshore wind development. The plan is intended to reflect the research and data collection needs of RWSC’s four Sectors with input from the science community. The plan will provide a path forward to ensure appropriate data collection protocols and standards are in place to support scientific research; this document can also provide a framework that can aid RWSC participants in coordinating and aligning funding to carry out necessary scientific activities.

This plan benefits greatly from the contributions of RWSC Bird & Bat Subcommittee members; researchers, managers, and other practitioners who joined Subcommittee calls; and the many scientists who conducted research or developed reference materials referenced throughout this plan.

Following this introduction, the first section of the chapter discusses the species of birds which occur within the RWSC Study Area. The species section is followed by a brief section summarizing primary sources of information about species’ distributions. The next section of this chapter discusses potential effects (negative or positive) of offshore wind development on bird species. The following section summarizes common field research methods for the study of birds, with a focus on the offshore environment. The subsequent section addresses the major research topics relevant to birds in the context of offshore wind development. The remainder of the chapter addresses recommended science actions of value to the four sectors that make up RWSC (state and federal agencies, eNGOs, and the offshore wind industry), in the context of recent, ongoing, and pending scientific activities relevant to recommended actions.

F.2 Species

This chapter addresses bird species (Class Aves) which could be at risk from offshore wind development occurring in the Northwest Atlantic within U.S. waters.  For the purposes of this plan, the geographic area of interest comprises the Atlantic Coast of the United States, extending from Maine’s northern border with Canada south to the Florida Keys, and from coastal areas extending 200 nm east into the ocean, including state waters (3 nm from shore) and federal waters of the Outer Continental Shelf (3-200 nm). This area is referred to in this plan as the RWSC Study Area. 

Hundreds of bird species occur within this area.  At least 416 native species are regularly found in the 14 coastal states of the U.S. Atlantic Coast, based on state eBird lists, U.S. Atlantic Coast ranges in Birds of the World, and Information for Planning and Consultation (IPaC) identifications of birds using North Atlantic offshore areas.  Many of these bird species inhabit the RWSC Study Area throughout the year.  Others may occur in this area exclusively during the breeding or nonbreeding season, or utilize the Atlantic Flyway for migratory movements between Canada and the Caribbean, Central America, and South America (AFSI, 2015; Newton, 2007; USFWS, 2023a).

A number of these species can be expected to experience impacts from offshore wind development, including collision fatalities, displacement, attraction, barrier effects associated with avoidance, and effects on abiotic habitat features and prey populations (SEER, 2022); indirect effects of offshore wind energy development, like climate change mitigation, can also be expected. While the focus of this plan is on offshore impacts of offshore wind development, potential onshore impacts of offshore wind on bird species are also possible. For example, excavation efforts where transmission cables are coming ashore from offshore facilities could affect beach-nesting birds. Therefore, bird species which primarily or solely occur in the onshore environment along the U.S. Atlantic Coast are also included within the scope of this plan, although they are not the focus of the bulk of this chapter.

All 416 species that occur in the RWSC Study Area are included in RWSC’s Bird List, a spreadsheet intended to be updated regularly to provide a complete listing of and basic information about the current regulatory and conservation status of relevant bird species, as well as characteristics relevant to exposure and vulnerability to offshore wind impacts. Vagrants, rare visitors to U.S. Atlantic waters, and non-native species are not included in the list.

For additional summary information about the types of birds that occur in the RWSC Study Area, see RWSC’s Bird Descriptions by Category [forthcoming in 2024]. Bird “categories” are loosely based on taxonomy, but also incorporate considerations relevant to offshore wind. This resource provides basic information about categories of birds and their life histories as relevant to their exposure and potential vulnerability to offshore wind development.  These sections also address other conservation threats facing these species, which could be of interest in investigating potential impacts of offshore wind or offsetting its effects. Species at particular risk from offshore wind development due to their life histories or conservation status are highlighted.

Within this plan, some science recommendations are discussed within the context of five subregions of the RWSC Study Area: the Gulf of Maine, Southern New England, New York/New Jersey Bight, U.S. Central Atlantic, and U.S. Southeast Atlantic (see Chapter 1). Avian assemblages and ecology may vary considerably over this geographic area. The Gulf of Maine subregion, located at the northern edge of the Study Area, with deeper water depths and a complex coastal topography (many islands, peninsulas, and inlets), includes a suite of species adapted to colder waters and more northern climes. Several alcid species breed along the Maine coast but are not found breeding in other states; colonies of breeding Arctic Terns and Black Terns, likewise, are only found in Maine. At the opposite end of the Study Area, many birds of more tropical regions, like whistling-ducks, Limpkins, and American Flamingos, are only found in Florida.

F.2.1 Regulatory Status

Many bird species are protected via federal regulations.  Important and relevant federal laws include the following:

Endangered Species Act (ESA).Currently 16 bird species that regularly occur in the RWSC Study Area are listed as Threatened or Endangered under the federal ESA (see RWSC Bird List), including two shorebird species (the Piping Plover, Red Knot) and three seabirds (Roseate Tern, Bermuda Petrel, Band-rumped Storm-petrel). In addition, the Black-capped Petrel has been proposed for listing as Threatened (USFWS, 2023b). The ESA places strict limits on the import, export, sale, possession, transportation, or “take” of listed species, with “take” defined as “to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct.” The ESA also allows for the designation of critical habitat for a species and prohibits the destruction of that habitat.

Migratory Bird Treaty Act (MBTA). Nearly all the birds that occur in the RWSC Study Area are afforded protection under the MBTA (see RWSC Bird List). The MBTA was enacted in 1918 to implement four international conservation treaties that the U.S. entered into with Canada, Mexico, Japan, and Russia (several of which were amended in more recent years). The MBTA covers over 1,000 bird species and is intended to ensure the sustainability of their populations. The MBTA prohibits the take (including killing, capturing, selling, trading, and transport) of protected migratory bird species without prior authorization by the USFWS. Of greatest relevance to offshore wind development is the prohibition of incidental take, that is the taking or killing of migratory birds that results from, but is not the purpose of, a lawful activity (USFWS, 2021). The USFWS prioritizes for enforcement incidental take that results from activities by a public- or private-sector entity that are otherwise legal and foreseeable, and occurs where known general or activity-specific beneficial practices were not implemented (USFWS, 2021). The USFWS is currently in a rulemaking process as the Service considers developing proposed regulations to authorize the incidental take of migratory birds (USFWS, 2023b).

Bald and Golden Eagle Protection Act (BGEPA).The BGEPA is more limited in scope than the two proceeding regulations. It protects Bald and Golden Eagles, both of which occur in the RWSC Study Area, prohibiting take of individuals, as well as their parts (e.g., feathers), nests, or eggs. The Act defines “take” as “pursue, shoot, shoot at, poison, wound, kill, capture, trap, collect, molest or disturb.” Regulations further define “disturb” as “to agitate or bother a bald or golden eagle to a degree that causes, or is likely to cause, based on the best scientific information available, 1) injury to an eagle, 2) a decrease in its productivity, by substantially interfering with normal breeding, feeding, or sheltering behavior, or 3) nest abandonment, by substantially interfering with normal breeding, feeding, or sheltering behavior” (50 CFR 22.6).

In addition to federal regulations, most states maintain a list of rare species which are afforded special protections under a state-level Endangered Species Act or other state statute. Over 150 bird species are protected by these state laws in the 14 states of the RWSC Study Area. Individual State Wildlife Action Plans also identify Species of Greatest Conservation Need (SGCN) which serve as foci for research and conservation efforts. At least two-thirds of U.S. Atlantic Coast birds are listed as SGCN in one or more states (see RWSC Bird List).

F.2.2 Defining Focal Species

While some scientific research methods will provide information about a variety of taxa (e.g., aerial surveys), other research methods (e.g., tagging) must by nature be species-specific. Since over 400 bird species occur regularly or occasionally in the 14 states of the U.S. Atlantic Coast, it is not practicable to study all these species using species-specific methods. For certain purposes, therefore, there is a need to identify birds which should serve as focal species for species-specific field research studies and other scientific activities.

In developing a framework to guide identification of focal species for these types of studies, the RWSC Bird & Bat Subcommittee began with criteria identified in a NYSERDA Stakeholder Workshop (Gulka and Williams, 2020). Through Subcommittee discussions, the list of criteria was slightly expanded to read as follows. Focal species could include:

  • Threatened and endangered species (federal and/or state-listed)

  • Species otherwise designated as of conservation concern (e.g., Species of Greatest Conservation Need [SGCN] in State Wildlife Action Plans, regional SGCN [Northeast and Southeast], state-listed “special concern” species, or proposed/candidate endangered species)

  • Other federally regulated species (i.e., species protected under MBTA or BGEPA)

  • Surrogates for rare species, which may be the best available proxy to study and understand rare species’ movements, behaviors, or expected effects of offshore wind development. (The Subcommittee recognizes that there are not perfect surrogates for the rare species themselves, but for some rare species, using a surrogate may be the best available option.)

  • Species or taxa known or suspected of being sensitive to impacts from offshore wind development due to existing information and/or aspects of their life history which might render them susceptible to offshore wind. (Existing information could come from pilot studies in North America, or from longer-term studies in Europe, where more research has been conducted to date. Life history aspects that inform risk could include foraging strategy, flight height distributions, sensitivity to other anthropogenic disturbances, or overlap between areas of high densities for a species and Wind Energy Areas). Focusing on species for which significant impacts are anticipated can increase the likelihood of having the power to detect change in a given study or studies (NYSERDA ETWG, n.d.).

  • Within a taxon or guild anticipated to be sensitive to offshore wind, species with high levels of existing baseline data, and whose population parameters (e.g., productivity, survival) can more easily be measured.

  • Species or taxa for which very little is known about potential impacts, because there has not yet been significant offshore development in their habitats (e.g., pelicans).

As noted previously, at least two-thirds of bird species that occur in the RWSC Study Area are listed as Species of Greatest Conservation Need in one or more states. This categorization therefore is not particularly helpful in developing a limited list of species for consideration as focal species. In addition, the category of “other federally regulated species” includes species protected under the Migratory Bird Treaty Act. The regulation covers nearly all bird species in the RWSC Study Area, with the exception of some species in the Orders Gruiformes and Galliformes.  This protection is important from a regulatory and conservation standpoint, but it is not helpful in developing a priority list of focal species.

Geography is important to consider when identifying focal species. Species distributions, abundance, and seasons of occurrence vary broadly across the five subregions of the RWSC Study Area. These differences are important to consider when identifying focal species for species-specific studies within a given subregion. If a particular marine bird or shorebird, for example, only breeds within one or two subregions, these areas will naturally be the focus for breeding season studies. In addition, it may be important to focus studies in certain subregions where a species of interest is most common and abundant, so as to obtain a sufficient sample size The state listing status of a species and associated level of conservation concern may also vary by state and is important to factor into decision-making.

This Science Plan recommends that the RWSC Bird & Bat Subcommittee develop and maintain a shared bird exposure/risk vulnerability matrix to aid in the periodic prioritization of focal species by geography, lease area, and research topic (see Section 6).

F.2.3 Regional Coastal and Offshore Distribution Information

This section addresses sources of mapped bird distributions in coastal and offshore environments which span the entire RWSC Study Area region. The resources detailed below have been developed based on data drawn from many smaller-scale studies and incorporated into larger databases or (in the case of defining critical habitat) collated as part of regulatory review.

In addition to these sources, many individual organizations and researchers collect and analyze bird distribution data relevant to one or more species for use at a local, state, or subregional scale. For example, many states survey nesting birds (including shorebirds and marine birds) and some, like New York, maintain a Breeding Bird Atlas.  The USGS and Environment Canada maintain data from the North American Breeding Bird Survey (BBS), covering the continental U.S. and Canada. Some of this information is also captured in National Audubon efforts, including the Christmas Bird Count and Important Bird Areas.

A compilation of all of these individual sources of bird distribution data is outside the scope of this Science Plan.  However, this plan includes recommendations to include all newly collected survey and tracking data in regional databases, as well as recommendations for further compilation of historic data into these databases (see Section 6).

F.2.3.1 Marine Bird Distribution Maps

One of the most comprehensive analyses of marine bird distributions in the RWSC Study Area was conducted by Winship et al. (Winship et al., 2018). Over 30 years of survey data contained in the Northwest Atlantic Seabird Catalog database, along with Eastern Canada Seabirds at Sea data from Canadian Wildlife Service, were analyzed using spatial predictive modeling to derive seasonal maps of the spatial distributions of 47 marine bird species in U.S. Atlantic Outer Continental Shelf and adjacent waters from Florida to Maine. Model predictions are presented as seasonal maps of the relative density of each study species, indicating where they are anticipated to be more or less abundant.  The analysis was designed to provide relative density, and does not purport to estimate the actual number of individuals/density of a given species that would be expected in any specific location. The maps were reviewed by experts with experience and knowledge of marine birds in the study area and their comments were incorporated into the accompanying report.

Through funding from BOEM, these maps were updated by NCCOS between 2020-2023 . As an additional component of this project, predicted changes in oceanographic conditions were used to project changes in distribution of several marine bird species in the context of climate change.

F.2.3.2 eBird Maps

eBird is a project of the Cornell Lab of Ornithology and collaborators which collects and analyzes information about bird sightings by expert and citizen scientists in terrestrial and marine environments. Birders enter when, where, and how they went birding, and then fill out a checklist of all the birds seen and heard. In some cases, data submitters may be following specific protocols, such as that of the International Shorebird Survey. The eBird Science team uses statistical models and machine learning to analyze patterns of abundance, distribution, and migratory movements. Raw eBird data are combined with high-resolution satellite imagery from NASA, NOAA, and USGS to estimate population trends and to predict distribution and abundance of bird species for every week of the year.

Because these data are often collected based on incidental observations and include limited offshore data, the marine bird distribution maps described above are considered of greater value for the marine birds included in that analysis than eBird maps. eBird data are nevertheless valuable for species not modeled in the maps described above. Additionally, they can provide valuable information about coastal distributions of marine birds, shorebirds, and other species.

F.2.3.3 Tracking Data

Motus and Movebank are two databases that house data collected from automated VHF tagging/tracking and other types of tagging/tracking respectively. These databases provide centralized locations for viewing tracking data from multiple studies, although summary products are fairly simplistic and comprehensive analyses of bird distributions are not available through these sites. They are described in more detail in Recommended Database Summaries.

F.2.3.4 Identified Critical Habitat

For bird species listed as Threatened or Endangered under the federal Endangered Species Act, the USFWS is required to determine whether there are identifiable areas that meet the definition of “critical habitat” (USFWS, 2003). Critical habitat is defined as:

  • Specific areas within the geographical area occupied by the species at the time of listing that contain physical or biological features essential to conservation of the species and that may require special management considerations or protection; and

  • Specific areas outside the geographical area occupied by the species if the agency determines that the area itself is essential for conservation.

There are 16 bird species occurring along the U.S. Atlantic that are identified as Threatened or Endangered across some or all of their range. In addition, the Black-capped Petrel has been proposed for listing as Threatened. Of these species, most either do not have critical habitat defined, or identified habitats do not occur in coastal areas. Defined critical terrestrial habitats could be relevant to where cables come ashore to connect to grid infrastructure, but are not broadly relevant to offshore wind infrastructure development. Critical habitat for the five listed and one proposed shorebird and marine bird species that occur along the Atlantic Coast is summarized below:

  • The Atlantic Coast breeding population of Piping Plovers is considered Threatened. Critical habitat for the wintering population of Piping Plovers along the U.S. Atlantic Coast was designated in 2001 and updated in 2008 (USFWS, 2008).

  • A new definition of critical habitat for the Threatened Red Knot was proposed in April 2023. The proposed revised definition includes coastal areas of Massachusetts, New York, New Jersey, Delaware, Virginia, North Carolina, South Carolina, Georgia, and Florida, which are described in detail here.

  • The northeastern breeding population of the Roseate Tern is considered Endangered; it occurs through much of the RWSC Study Area, from Maine south to South Carolina (breeding Maine to New York). The Caribbean breeding population, which is considered Threatened, occurs north into the Florida Keys. No critical habitat has been defined for this species.

  • No critical habitat has been defined for the Bermuda Petrel or Band-rumped Storm-Petrel, both of which nest outside of the RWSC Study Area.

  • The Black-capped Petrel has been proposed for Threatened status. No critical habitat has been defined for this species.

F.3 Potential Effects of Offshore Wind on Birds

Offshore wind development and operations could have positive, negative and/or mixed impacts on birds. Many of the hypotheses about how offshore wind development will affect North American bird species are drawn from research in Europe, where offshore wind facilities have been in place and under study for longer time periods. For a recent review of European avian offshore wind studies through 2019, see Fox and Petersen (Fox and Petersen, 2019). For a brief summary of anticipated impacts to North American birds, see Bird and Bat Interactions with Offshore Wind Farms (NREL and PNNL, 2022). This section briefly summarizes the range of potential effects of offshore wind development on birds. For an up-to-date list of recently published literature on this subject, search the Tethys Knowledge Base.

Offshore wind farms could affect birds through a variety of mechanisms. Injuries or fatalities could occur directly through collisions with infrastructure, such as offshore wind turbine blades, towers, meteorological stations, electrical service platforms, or other facility infrastructure (Johnston et al., 2014), or via collisions with boats accessing offshore facilities as part of construction and operations activities.

Birds could also be affected in less direct ways through changes in the local environment caused by the presence of offshore wind facilities. These impacts could occur via many mechanisms, including the physical presence of turbine infrastructure, increased lighting, changes in sound (including infrasound), changes in pressure, changes to local electromagnetic fields, effects on prey species, or effects on how humans use the area of the wind facility.  These changes in the local environment could lead birds to be attracted to or avoid offshore wind facility infrastructure at the macro-, meso-, or micro-scale (Dierschke et al., 2016). For example, phototaxis, the attraction of birds to lit structures (Adams et al., 2021), could attract birds to lighted offshore wind infrastructure or boats, increasing collision risk as well as changing movement patterns and distributions. Increased sound and infrasound could affect the hearing abilities of birds both above and below the water’s surface, with potential impacts on foraging, navigation, intraspecies communication, or predator avoidance (Anderson Hansen et al., 2020; Mooney et al., 2019; Patrick et al., 2021). Increased vessel traffic could increase anthropogenic disturbances of some bird species (Burger et al., 2019; Schwemmer et al., 2011).

Macro- and meso-scale avoidance of offshore wind turbines could lead to habitat loss or degradation. Habitat displacement effects caused by offshore wind facilities have been observed in a variety of bird taxa, @dierschke2016. Habitat degradation could occur if birds are less comfortable foraging within a wind facility, foraging efficiency is lower near turbine infrastructure, and/or the presence of the turbines cause stress levels to be higher, reducing birds’ physiological condition. Habitat connectivity could also be reduced via avoidance, although connectivity impacts are more likely to be a concern when considered cumulatively at the scale of multiple wind facilities (Masden et al., 2009). Meanwhile, some species, such as cormorants, show attraction to turbine structures (Dierschke et al., 2016). Certain bird species may therefore benefit from increased roosting and foraging opportunities around turbines – although offshore wind facilities could also serve as ecological traps if attraction increases collision risk.

Offshore wind facilities may alter inter-species interactions in ways that benefit or negatively impact birds. For example, the artificial reef effect might alter fish distributions, affect local fish populations, concentrate forage fish around turbine foundations, or otherwise alter the ecology of prey species (Degraer et al., 2020). Changes in the distribution patterns or abundance of forage fish could increase or decrease the forage quality of certain habitats, bring one bird species into greater proximity to a competitor for the same food sources, or concentrate animals in a way that increases risk of disease spread. Human interactions with birds might also change in the presence of offshore wind infrastructure – for example, if an artificial reef effect of turbine structures brought more recreational fishing into areas of high marine bird density, entanglement in fishing gear could become more frequent.

The above focuses on offshore effects of offshore wind. Of course, activities such as trenching for cables at coastal sites and construction of transmission corridors to connect offshore facilities with onshore grid infrastructure are land-based components of offshore wind development that could affect species that frequent shorelines and inland habitats. Clearing of transmission corridors and installation of transmission lines have consequences for birds, including the potential for habitat loss, degradation, or creation, depending on the species (Askins et al., 2012; Martin et al., 2022). Because transmission corridors are not novel development types in the United States, have been the subject of past research, are addressed by current environmental laws, and represent a small area of impact relative to the footprint of offshore wind facilities, they are not the focus of this section or this chapter. However, they represent a potential source of impact that certainly must be evaluated as part of the environmental review of any wind facility.

On a global scale, the development of offshore wind facilities could serve as a major component of the transition away from fossil fuel use, reducing greenhouse gas emissions and mitigating climate change (Barthelmie and Pryor, 2021). The mitigation of climate change is a major conservation action affecting many bird species, including those that breed or forage at high latitudes (Bateman et al., 2020). Because oil spills and other pollution-related impacts from fossil fuels are major stressors for many marine birds (Troisi et al., 2016), moving to a clean energy framework could also reduce direct impacts from fossil fuel use.

Offshore wind development could indirectly benefit avian species if wind facility developers implement effective voluntary off-site mitigation efforts, conducted in such a way and to such an extent that they actually provide a net benefit to species’ populations. Off-site mitigation planning is discussed later in this chapter. In addition, a greater scientific interest and research focus on certain species in the context of offshore wind development might lead to a better scientific understanding that elucidates unrelated conservation issues and opportunities and ultimately better serves these species.

F.4 Common Data Collection Methods and Approaches

A wide variety of scientific methods are used for studying birds in coastal and offshore environments, which are summarized below. This section is intended to provide a brief description of different study methods, rather than a detailed assessment of the pros/cons and current state of development of each technology/methodology. For tracking of new technologies, see the Tethys database of monitoring technologies.

Note that this brief review focuses on technologies or methods which can be used in the offshore environment or at coastal/island nesting sites of seabirds and shorebirds. There are many additional survey techniques and protocols used in the onshore environment. These are relevant to the study of terrestrial effects of offshore wind – such as effects of trenching for cables where they are brought ashore, or clearing of transmission corridors to connect offshore wind with onshore grid infrastructure – but for the sake of brevity and a focus on novel offshore issues, they are not addressed here.

F.4.1 Observational Surveys

At-sea aerial surveys for seabirds were historically conducted using airplanes flying at roughly 60-200 m over the ocean surface, with live observers recording observations within a certain distance from the line of transect. In more recent years, some at-sea surveys have transitioned over to the use of aerial photos or videos, including high-definition photos or video, which can be conducted at a higher flight altitude. High-definition aerial photography has some advantages over live observers, including reduced bird disturbance due to the higher flight altitude, less effect of observer bias, and the availability of raw data for quality control and future re-analysis.  In addition, there is some evidence that aerial video can cover a larger area, provide greater spatial accuracy, lead to higher numbers of sightings, and more frequently identify birds to species (Žydelis et al., 2019). Of greatest importance to offshore wind studies is the higher flight altitude – conducting at-sea surveys at no more than 100 m over the ocean surface will not be possible at offshore wind facilities once turbines are installed. In order to be able to accurately compare before/after survey results in the vicinity of offshore wind facilities, high-definition aerial photography (still photos or video) are recommended for all offshore surveys of seabirds moving forward. 

Censusing birds at sea is the primary objective of this research method; however, flight height estimates can in some cases be gleaned from the data. In addition, with digital aerial photographs, or particularly video, it is sometimes possible to identify obvious behaviors, like foraging dives. However, even with video, recordings are only brief (e.g., 6-8 frames of a bird over 1 second), and therefore not particularly informative regarding behavior.

Boat-based surveys can also be used to inventory/census bird species present at sea. At smaller spatial scales, they can be more cost-effective than aerial surveys. They can provide a higher level of accuracy in identifying species, age, and behavior of seabirds at sea (Camphuysen et al., 2004). As lease areas become larger and locations further offshore, aerial surveys may naturally become more cost-effective and more common. While all study methods have some biases, boat-based surveys tend not to be as good as aerial surveys for detecting some taxa – particularly seaducks and loons, which can be disturbed by boats (Camphuysen et al., 2004).

Boat-based or stationary (e.g., turbine platform-based) observations using live observers can also be used to estimate flight height and collect behavioral data, such as documenting foraging behavior or responses to turbines.

In coastal areas and on islands, population surveys of colonial nesting seabirds, long-legged wading birds, or shorebirds are common. These surveys are sometimes aerial (Bakó et al., 2014) (using aerial still photographs or video), or may be ground-based, including surveys at nesting colonies to census the entire population at a particular site and, in some cases, to assess survival of marked individuals. At nesting sites, other observational studies may also be conducted, including nest monitoring to document nest productivity over time, behavioral studies, and observations of adults feeding young to document diet.

Incidental observations can also provide useful information about species presence and behavior, particularly for those infrequently observed at sea. Citizen science can also be used to collect these types of data – eBird is one database that capitalizes on this type of data to generate useful information about timing and distributions of bird occurrence, although offshore data of this type are quite limited.

F.4.2 Radar and Lidar

Radar systems (RAdio Detection And Ranging) come in a range of types, sizes, frequencies, and modes of action, which affect the spatial and temporal scales of detection, resolution, and types of data collected. They detect birds by emitting pulses or continuous streams of radiowaves which are scattered from any object encountered, producing an “echo” in returned energy which is detected and interpreted by the radar equipment. They can be used to study a variety of aspects of avian ecology (Hüppop et al., 2019).

NEXRAD (WSR-88D) towers are large, S-band, Doppler weather radar stations deployed across the United States to provide information on a broad set of weather conditions, including precipitation and wind speed (Diehl and Larkin, 2005). These radars have a lower resolution than some, but can detect flocks of birds, including migrants leaving stopover sites for high-altitude nocturnal flights in the spring and fall, trans-Gulf of Mexico movements, and broad- and narrow-front migrations. They have been used to identify stopover, passage, and roosting areas (Buler and Dawson, 2014; Chilson et al., 2019), as well as to study changes in total bird abundance (measured as biomass) and phenology over time (Chilson et al., 2019; Horton et al., 2020; Rosenberg et al., 2019). In addition, there are applications for behavioral ecology describing flight speed, direction, orientation, and altitude. NEXRAD coverage does extend offshore in some portions of Atlantic coast, but the radar beam typically samples altitudes above most bird migration in this region. BOEM is currently funding a study to create a database of terrestrial migrating birds moving to and from the offshore environment including through use of NEXRAD along the U.S. Atlantic Coast. Note that Canadian weather radars deployed in the maritime provinces could also provide data valuable for studies at the northern end of the RWSC Study Area.

X-band radars use smaller antennae and have a smaller spatial range. They operate using a shorter wavelength, and hence have a higher target resolution. These radars also scan the atmosphere more regularly, increasing temporal resolution. Mobile X-band radar units can be deployed on coastal and island sites, boats, or offshore infrastructure to monitor for passage rates of commuting or migrating birds. They cannot identify animals to species, but can provide information about wingbeat frequency and body size, which can inform classification, as well as information about flight height, direction, and speed.

Many ships are equipped with S-band or X-band radars (or both) to aid in navigation, with S-band systems providing longer-range data and better functioning in fog, and X-band radars, as noted above, providing greater precision. These “marine” radars can also be used to detect birds, with precise applications and data dependent on the type of system.

The use of portable radars for avian research offshore is currently being explored through a BOEM-funded study.

Lidar (Light Detection and Ranging) systems work by a similar mechanism, but use a different frequency on the electromagnetic spectrum. In this technology, a laser beam is emitted, which bounces back after it encounters an object. Lidar systems are more precise than radar, but operate over a shorter range, and are obstructed by fog or rain (Bilik, 2023). The use of this technology for measuring bird flight height is effective offshore and can be accurate to within 1 meter (Cook et al., 2018). Cook et al. (2018) provides recommendations on use, but uncertainties remain regarding Lidar capabilities for wildlife monitoring, particularly for detection of small-bodied birds (Sloan and Schultz, 2023).

F.4.3 Acoustics

Acoustic surveys using acoustic detectors (a combination of microphones and recording devices) to record calls of birds are becoming increasingly common (Pérez-Granados and Traba, 2021), although they remain more frequently used for bats. This method of monitoring can provide information about migration phenology, species composition, acoustic soundscapes for communication, and, in some cases, numbers of passing individuals. Acoustic surveys for birds in the offshore environment are most commonly used for night migrants (Hill and Hüppop, 2008), and typically use passive, stationary detectors configured to sample primarily in the audible frequency range (e.g. 1-12 kHz). Passive surveys offshore utilize stationary detectors deployed on ocean buoys, meteorological towers, offshore wind turbines, other offshore infrastructure (such as electrical service platforms [ESPs], also commonly referred to as offshore substations [OSSs]).

Acoustic surveys are only effective when study animals are vocalizing. Ambient noise can interfere with detection of vocalizing animals and limit the distance over which calls will be recorded, an important factor to consider in deploying acoustic detectors on operating turbines.  Challenges also remain in differentiating among flight calls of different species (“Bioacoustics data analysis a taxonomy, survey and open challenges,” 2020; Priyadarshani et al., 2018). However, software for the detection, classification, and analysis of field-collected audio files continues to be improved (Van Doren et al., 2023a). Some new software can address suboptimal signal-noise ratios and evaluate areas of masking interference to speed and to refine analyses (Van Doren et al., 2023b). The extent to which acoustic survey technologies can be counted upon to operate continuously in harsh offshore conditions also requires further evaluation.

F.4.4 Banding, Tagging, and Tracking

Capture-mark-recapture studies can be used to assess population size, evaluate survival, and study migratory movements of long-ranging birds. Bird banding is a very common practice for birds of all sizes, with banding information typically going to a central repository, the Bird Banding Laboratory (BBL). (Note that the BBL database cannot handle data on birds that are not fit with metal USGS bands, which includes most piping plovers on the Atlantic Coast. Those data are instead housed locally on project-level databases.)

There are a variety of different types of tags which can be attached to birds to gather information about their movements. Birds can be outfitted with geolocator tags, which measure daylight versus time, allowing for estimates of latitude and longitude, approximating bird positions. An advantage of these tags is that they are very lightweight. However, they have an accuracy range of only ± 200 km, and the animal must be recaptured in order to retrieve the data.

GPS dataloggers receive information from a satellite system known as the Global Positioning System, which is maintained by the U.S. government (Smithsonian Institute, 2023). Wherever a GPS receiver has unobstructed line-of-sight to four or more GPS satellites, it can use the information transmitted by the satellites to calculate accurate time and location. GPS dataloggers are set to record data at regular intervals (rather than continuously) to generate a dotted movement track. In order to access the data, the animal must be recaptured and the tag recovered. Alternatively, GPS receivers can be paired with a transmitter that sends the data to a particular server, which can be a satellite system (for global coverage) or cellular phone system (where cell tower coverage is expected to be available). For these types of tags, the animal does not need to be recaptured; however, the use of a transmitter requires a larger battery, which means that they cannot be deployed on smaller bird species. Geofencing is the practice of creating a specific study area defined by a virtual perimeter; this methodology can allow for the collection of a higher frequency of recorded GPS data locations within wind facility boundaries.

Satellite tags are also deployed on birds. Platform Transmitting Terminals (PTT) tags send periodic messages to a global satellite system called Argos, which is dedicated to ecological and environmental research (Smithsonian Institute, 2023). Argos Service satellites pick up and store signals, relaying them in real-time back to earth, where data are processed and delivered to researchers. As with GPS transmitters, battery size currently limits the size of bird on which these tags can be deployed. Spatial uncertainty of Argos data is 250 m to >1500 m, and flight height data cannot be recorded; thus, these data are less accurate than GPS data.

VHF (Very High Frequency) and UHF (Ultra High Frequency) radiotags transmit signals in the radio frequency range, which can be detected with a receiver. These types of tags are regularly deployed on birds. Historically, tags with different frequencies were deployed on animals within one research study to allow for easy identification of different individuals. The animals were then tracked, often via manual telemetry with a hand-held receiver. Manual tracking could be conducted on-foot, using a vehicle, boat, or aircraft. Study animals could also be tracked via a receiver attached to a stationary tower with antennae pointed in multiple directions, which could be automated to detect signals periodically or rotated manually by a researcher to detect a signal with an associated bearing. Manual telemetry is limited by the search effort available for finding and pinpointing the radio signal, and hence faces significant challenges in tracking animals that range over long distances.

In recent years, the development of the Motus Wildlife Tracking System has allowed for much more widespread use of coordinated automated radiotelemetry for tracking of wide-ranging and/or migrating birds. This system relies on coded radiotransmitters which all operate on one of two common frequencies, but which emit unique ID codes to identify different individuals. Signals from the tags are received by a network of automated radiotelemetry stations consisting of antennas, a receiver, a power source, memory storage, and sometimes data transmission infrastructure.  Telemetry stations can be deployed on land, on coastal locations, or on offshore infrastructure, including ocean buoys and offshore wind turbine platforms. Advantages of this system include that tags are small and stations deployed by one research group can detect passage of animals by other researchers operating in the same network, allowing for development of a widespread network with more likelihood of detecting wide-ranging study animals. This system also has the distinct advantage over manual telemetry that signals can be monitored for continuously. Motus system technology has limitations, including limited range of some telemetry stations (typically 15 km) and, in most cases, an ability to determine only general proximity or bearing from the station rather than precise location. Efforts to improve triangulation capabilities are underway (see Section 6). Offshore wind developers are including deployment and maintenance of Motus stations, as well as tag deployment, as part of Avian Monitoring Plans developed for review by BOEM and USFWS. Motus station deployment and research efforts in the U.S. Atlantic are coordinated through the Atlantic Offshore Motus Project.

F.4.5 Bird-Turbine Interaction & Collision Detection Systems

On turbine platforms, turbine nacelles, or other offshore infrastructure, cameras can be used to record bird presence and behavior in the vicinity of turbines, which can inform when and where animals are present in portions of the rotor-swept zone and document bird interactions with turbines, including perching, roosting, attraction, micro-avoidance, lack of response, or collisions. Cameras differ in their mode of action, resolution, and the frequencies of electromagnetic radiation they use, from conventional cameras that operate in the visual range, to so-called “infrared” cameras that operate in the near infrared range, to so-called “thermal” cameras that operate in the far infrared range. Continuously operating cameras provides unique information about bird behavior in the vicinity of wind turbines. These systems can also be employed in conjunction with other sensors (e.g., acoustics, radar) to deliver additional information about behavior or collisions (see below). However, many of these systems are expensive at present and often only deployed at one or a few turbines in a study area. The field of view of a particular camera is often not sufficient to encompass the full rotor-swept zone, at least with sufficient granularity to identify birds throughout that zone. The extent to which these technologies can be counted upon to operate continuously in the harsh offshore environment is currently being evaluated.

At onshore wind facilities, carcass surveys are commonly used to document mortality and estimate fatality rates for a variety of bird species that collide with wind turbines. Offshore, carcasses of individuals can be expected to fall into the ocean in most instances and so collision detection systems are needed. Collision detections systems may incorporate visual range, thermal, or infrared cameras as described above (Happ et al., 2021), as well as acoustic detectors, radar systems, and/or accelerometers for impact detection. Over a dozen multi-sensor systems for documenting collisions and other bird interactions with wind turbines are under evaluation or currently in use at wind facilities (Dirksen, 2017; NREL and PNNL, 2022), and at least three have been deployed on offshore turbines (Lagerveld et al., 2020; Mark Desholm, 2003; Tjørnløv et al., 2023; Willmott et al., 2023). Efforts are currently underway at land-based wind facilities to develop, improve, and validate collision monitoring technologies. At present, validation activities are limited to the terrestrial environment, where results can be compared with carcass searches.

There are a number of technologies in various stages of development or deployment intended for automated real-time identification of bird species or groups. In addition to monitoring uses, these can be integrated with active curtailment or deterrent systems. Technologies that have been tested in the offshore environment include Spoor and DT Bird.

Beach carcass surveys for the bodies of birds killed at offshore turbines have been proposed, but are only likely to be effective, if at all, in locations with very specific geographies and patterns of ocean currents. Occasionally, birds that collide with turbines may fall to the turbine platform. Birds may also collide with ships accessing wind energy facilities for construction or maintenance. Carcasses can be collected from turbine platforms, boats, and offshore infrastructure; when identified and documented, they provide incidental information about species’ occurrence in the marine environment, possible offshore wind facility impacts, and effects of increased vessel traffic in these areas.

F.4.6 Other Monitoring Methodologies

There are a range of tissue sampling methods from live-caught birds, or their feces, which provide a variety of information about individuals’ migratory status, diet, and health, as well as population-level genetic structure.  These include collections of feathers, blood, skin, stomach contents, and fecal matter, to variously conduct stable isotope analysis, physiological analyses (e.g., for stress hormones), diet assays, genetic analyses, or others (Cook, 2012; Robuck et al., 2021; Steenweg et al., 2017).

In addition to direct sampling of individuals, collection of DNA from the ambient environment (eDNA) also has the potential to provide information about species present marine areas (Closek et al., 2019; Zhang et al., 2020). This is a relatively new technology and the utility of this technique to address various research questions is not yet fully understood.

F.5 Research Topics: Birds and Offshore Wind in the U.S. Atlantic

Research questions about offshore wind development and wildlife are centered around two common themes. First, there is a need to measure, estimate, model, or otherwise assess the scale of impacts of offshore wind development on birds, in order to determine which impacts are significant at an individual, subpopulation, or population scale. Second, there is a need to understand how to address any impacts that may occur via effective mitigation. In the context of this chapter, “mitigation” is used broadly, as defined by the Council on Environmental Quality (CEQ) National Environmental Policy Act (NEPA) regulations (40 CFR § 1508.20).  Thus, mitigation in this context includes:

  • Avoiding the impact altogether by not taking a certain action or parts of an action. This could include strategies like siting wind facilities with setbacks from colonial breeding sites of birds of conservation concern or outside of areas with high densities of particular marine bird species.

  • Minimizing impacts by limiting the degree or magnitude of the action and its implementation. This could include strategies like implementing lighting regimes that minimize bird attraction to turbines.

  • Rectifying the impact by repairing, rehabilitating, or restoring the affected environment. This could include projects like stabilizing or revegetating areas affected where trenching occurred to allow for laying of a transmission cable.

  • Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action.

  • Compensating for the impact by replacing or providing substitute resources or environments. This could include off-site efforts like supporting predator control at a nesting site to increase populations of a breeding tern species that is affected by collision mortality.

The goal of mitigation measures could be to meet regulatory requirements to negate or offset any negative impacts of offshore wind development, or to meet voluntary goals of providing a net benefit to the species.

From the perspective of a regulator, conservationist, or offshore wind developer, the progress of research would ideally proceed from development of accurate and cost-effective technologies for wildlife monitoring, standardized systems for data collection and analysis, and understanding of baseline conditions, moving then to evaluation of impacts and mitigation strategies, and finally to widespread development of offshore wind in the context of implementation of effective mitigation measures. However, given the rapid pace of offshore wind development (U. S. Department of Energy, 2023), this slow and measured progression is not a realistic timeline. Rather, multiple areas of research will need to be advanced simultaneously. In the meantime, regulators must necessarily rely on the best available science, both in identifying areas that should be avoided in siting of wind facilities (mitigation via avoidance) and in assessing potential risks to protected and vulnerable species. Tools must continue to be developed to help inform these efforts. While many conservationists prefer focusing on earlier steps in the mitigation hierarchy (Arlidge et al., 2018), the reality is that the impacts of offshore wind development will not be fully evaluated until many hundreds of turbines are installed. This suggests that effective on-site and off-site mitigation measures will also need to be an early focus, because once turbines are in the water, they are unlikely to be removed or turned off completely. On-site mitigation options may be employed, where feasible. However, off-site mitigation to compensate for or voluntarily offset impacts may be the only viable option, in some cases, for addressing documented or probable impacts.

Research topics of interest for birds and offshore wind include:

  • Creating a structure in which to collaboratively conduct and share scientific research and advances, through discussion, coordination, and planning.

  • Improving data collection and distribution methods.  This includes standardization of data workflows, refinement of structures for data sharing, and technological advances.

  • Understanding baseline conditions of bird populations and bird ecology offshore. 

    • This includes addressing questions about how distribution patterns, density, and movements vary by time of year, with meteorological conditions, across seasons (i.e., breeding, migration, nonbreeding seasons), by sex, age, and reproductive status, with interannual variation, and especially in the context of global climate change.  Understanding distribution and abundance during the breeding season is of particular interest for colonial nesters that may be tied to only a few historic breeding areas. Movement metrics of interest include speed, distance and longevity of flights, flight height, and starting points and destinations.

    • This also includes assessing important variables relative to population dynamics (e.g., fecundity, survival, population structure) and interactions among bird species and with prey populations.

  • Informing pre-construction risk assessments of potential impacts to birds. This includes considering exposure of birds to offshore wind development, based on baseline distributions noted above. Collecting data to inform collision risk models and developing these models are also included.

  • Assessing impacts of construction and operation of offshore wind facilities. This includes assessing changes from baseline conditions (e.g., distribution patterns, movements, population dynamics and trajectories, ecological interactions) in the context of climate change and other environmental changes. It also includes documenting collision fatalities, where possible.

  • Evaluating on-site mitigation strategies. This could include mitigation activities effective during construction (e.g., noise reduction measures) or operation (e.g., painting turbine blades).

  • Identifying and evaluating off-site mitigation strategies. As noted above, due to the rapid pace of offshore wind development relative to the pace of research on impacts, off-site mitigation could represent an important aspect of offshore wind development, if significant impacts are found. These could be implemented to meet “no net loss” regulatory requirements or involve voluntary conservation offsets providing a net benefit to species.

Specific research questions are detailed in the Atlantic Offshore Wind Environmental Research Recommendations database, which summarizes data gaps and questions from a variety of peer-reviewed and technical report publications.

One recommendation of this plan is to reconcile broad research topics with specific research questions through the identification of focal species, major potential areas of offshore wind impact, and focal research questions by subregion and lease area (see Section 6).