Ocean Wind Power Ecological Baseline Studies Final Report - Volume 1: Overview, Summary, and Application

Report

Title: Ocean Wind Power Ecological Baseline Studies Final Report - Volume 1: Overview, Summary, and Application
Authors: Geo-Marine
Publication Date:
July 01, 2010
Pages: 259

Document Access

Website: External Link
Attachment: Access File
(17 MB)

Citation

Geo-Marine (2010). Ocean Wind Power Ecological Baseline Studies Final Report - Volume 1: Overview, Summary, and Application. Report by Geo-Marine Inc and New Jersey Department of Environmental Protection Office of Science. pp 259.
Abstract: 

The State of New Jersey is committed to finding long-term energy solutions and is pursuing alternative energy options. Offshore wind may provide a solution to New Jersey’s long-term energy needs. There are limited data and information on the natural resources and their environment occurring in New Jersey’s offshore waters, specifically the region being considered for wind turbine development. Geo-Marine, Inc. (GMI) was contracted to conduct a scientific baseline study by the New Jersey Department of Environmental Protection (NJDEP) Office of Science to fill major data gaps for birds, sea turtles, marine mammals, and other natural resources and their environments found in the Study Area.

 

The objective of this study was to conduct baseline studies in waters off New Jersey’s coast to determine the current distribution and usage of this area by ecological resources. The goal was to provide GIS and digital spatial and temporal data on various species utilizing these offshore waters to assist in determining potential areas for offshore wind power development. The scope of work includes the collection of data on the distribution, abundance and migratory patterns of avian, marine mammal, sea turtle and other species in the study area over a 24-month period. These data, as well as existing (historical) data, were compiled and entered into digital format and geographic information system (GIS)-compatible electronic files. Those portions of the study area that are more or less suitable for wind/alternative energy power facilities were determined based on potential ecological impact using predictive modeling, mapping, and environmental assessment methodologies.

 

Field studies were initiated in January 2008 and continued through December 2009. Data for avian abundance, distribution, and behavior were collected by shipboard surveys (offshore and coastal), aerial surveys, radar surveys (offshore and coastal), Next Generation Radar (NEXRAD) and Thermal Imaging-Vertically Pointing Radar (TI-VPR) studies, and supplemental surveys (shoal surveys and sea watch) were conducted over the 24-month period. Marine mammal and sea turtle data were collected via shipboard surveys, aerial surveys, and passive acoustic monitoring to assess the distribution, abundance, and presence of marine mammal and sea turtle species in the Study Area. Detailed information on the methods, data analyses, and results from these field studies is included in this document. In addition, a thorough review of fish and fisheries resources of the Study Area was conducted, which includes an overview of the ichthyofauna (including fish species designated with essential fish habitat [EFH]) of the Mid-Atlantic Bight (MAB) and the Study Area and the ancillary fishes observed during the shipboard and aerial surveys. A description of the federal- and state-level fishery management is presented for commercial and recreational fisheries, and the results of New Jersey fisheries independent bottom trawl data analyses are discussed.

 

In addition to the data collected on biotic resources, physical parameters within the Study Area were measured, including wind speeds, water temperature, salinity, depth, chlorophyll, and dissolved organic matter. Extensive literature searches were also conducted on climate, currents and circulation patterns, and other important physiographic components in effort to characterize the Study Area and gain understanding of the relationships between the physical and biological resources.

 

 

Avian Summary

SHIPBOARD AND SMALL BOAT SURVEYS

 

A total of 176,217 birds representing 153 species were recorded, with 84,428 birds of 145 species being recorded during the shipboard offshore surveys and 91,789 birds of 82 species recorded during the small-boat coastal surveys. Federally endangered, threatened, and candidate species were not detected during avian surveys. Fourteen of the 21 federally listed species of concern and 16 of the 20 state-classified endangered, threatened, and special concern species potentially occurring in coastal and offshore waters were observed during the survey.

 

Avian densities were highest near shore at all seasons, although this finding was much more pronounced in winter than in summer (ratio of abundance on offshore surveys vs. small-boat coastal surveys ranged from 2:5 to 1:5). This was because of the large numbers of coastal-breeding gulls and terns and wintering waterfowl along the New Jersey coast and the relative lack of true pelagic seabirds in the Study Area (although there were large numbers of Wilson’s Storm-Petrels (Oceanites oceanicus), an austral migrant from the Southern Ocean, present offshore in the summer). Overall, the areas of highest abundance were restricted to inshore waters, with the highest avian abundances recorded east of Hereford Inlet, south and east of Ocean City, and east of Atlantic City. Offshore, the most consistent area of high avian abundance was near a shoal area east of Barnegat Inlet. The summer seasons exhibited the lowest absolute abundance, with the majority (54.4%) of individuals detected being of locally-breeding species, primarily Common Tern (Sterna hirundo) and the three breeding gull species (Laughing [Leucophaeus atricillus], Herring [Larus argentatus], and Great Black-backed [Larus marinus]).

 

An interesting difference among the four seasons was that highest relative abundance was shifted quite noticeably from offshore in summer (56% or 37 of 66 highest-abundance blocks were offshore in the season) to nearshore in winter (3% or 2 of 65 blocks). Spring and fall are transitional seasons and were intermediate in this aspect (spring: 27.7%; fall: 18.5%). This variation was a result in differing habitat preferences between the seasonal avifauna, with the winter avifauna dominated by inshore-foraging species (e.g., scoters) and the summer avifauna dominated by offshore-foraging species (e.g., Common Tern).

 

Seasonally, species composition varied little between 2008 and 2009. Black Scoter (Melanitta nigra) was the most abundant bird in winter for both years, as was Northern Gannet (Morus bassanus) in spring and Laughing Gull in summer. In fall, Laughing Gull and Northern Gannet were the two most abundant species in both years. While numbers of many species fluctuated from 2008 to 2009, some of this change can be attributed to differences in survey timing between years. For example, in fall 2008, surveys were spaced rather evenly over the season, while surveys were concentrated at the beginning and end of fall 2009. Thus, species such as Surf Scoter (a mid-season migrant) that migrates through New Jersey in large numbers during mid-fall showed a large decrease in fall abundance from 2008 to 2009.

 

In addition to examining abundance and distribution, data were also analyzed to determine frequency of occurrence within the potential rotor-swept zone (RSZ) of power-generating wind turbines, defined as 100 to 700 feet (ft; 30.5 to 213.4 meters [m]). Of the >70,000 flying birds recorded, 3,433 (4.8%) occurred in the RSZ, with 33 species recorded in the RSZ at least once. More species occurred in the RSZ in fall (21 species) than any other season, followed by winter (16), spring (15), and summer (five). Scaup (Aythya spp.) accounted for 54.5% of all birds in the RSZ for the small-boat coastal surveys, and 31.8% of all birds in the RSZ overall. The only three species to occur in the RSZ in all four seasons were Northern Gannet, Herring Gull, and Great Black-backed Gull. Red-throated Loon (Gavia stellata), Common Loon (Gavia immer), Osprey (Pandion haliaetus), and Laughing Gull were recorded in the RSZ in three of the four seasons. Nearly all scaup in the RSZ (1,088 of 1,091) were recorded during a severe cold snap in January 2009, illustrating the potential effects of a major weather event on avian movements. Offshore, Northern Gannet was the species occurring most often in the RSZ (594 individuals), though the percentage of the species detected within the RSZ was small (3.9%)

 

AVIAN RADAR SURVEYS

 

Avian radar surveys were conducted at offshore locations over the Study Area in spring 2008, fall 2008, and spring 2009. Data collection was limited in fall 2008 and severely limited in spring 2009. Onshore radar surveys were conducted from three locations during 2008 and 2009.

 

Vertically scanning radar (VerCat) and horizontally scanning radar (TracScan) data from offshore and onshore were analyzed and data filters were developed to remove detections from rain (especially virga) and sea clutter, because these detections generate false tracks. Track counts were adjusted for dropped tracks that received a new track ID when the target was the same as the original track. The TI-VPR system sampled targets passing through a 20-degree (°) cone directed vertically to determine the proportion of each type of biological target (e.g., birds, bats, insects) detected by VerCat. The TI-VPR data were used to develop a correction factor for insects in the radar count data from the VerCat. Data from offshore barge-based and onshore-based observer validation surveys were analyzed and used to evaluate the results of radar analyses.

 

The VerCat flux value (adjusted bird tracks/cubic kilometer/hour [abt/km3/hour]) is the primary metric used to estimate potential bird-turbine collisions. Data related to cumulative diurnal and nocturnal flux were sorted by time period (weeks, daytime and nighttime) into three altitude bands with reference to the potential RSZ: (1) below the RSZ (low altitude band, 1 to 99 ft above mean sea level [AMSL]), (2) within the RSZ (middle altitude band, 100 to 700 ft AMSL), and (3) above the RSZ (high altitude band, 701+ ft AMSL) and by wind category (0-8 miles per hour [mph], 9-16 mph, and above 16 mph).

 

General overall conclusions and trends regarding bird flux altitude distribution are presented first and then are followed by a detailed summary of flux abundance within each altitude zone.

 

Offshore Flux

 

Spring 2008

  • Cumulative flux was greater during the day in the middle (RSZ) than in the low altitude band over both nearshore and offshore sampling locations.
  • During the night greater cumulative flux values occurred within the RSZ than below the RSZ as the spring season advanced for both nearshore and offshore grids.

During spring 2008, daytime cumulative flux values gradually decreased within the low altitude band (range: approximately 1,200-250 abt/km3/hour) and gradually increased within the RSZ (range: approximately 200-900 abt/km3/hour) as the spring season advanced for both nearshore and offshore grids. Cumulative diurnal and nocturnal flux in the high altitude band was 50-750 abt/km3/hour below the RSZ and from >150-300 abt/km3/hour above the RSZ. In spring during the night, the majority of movement below the RSZ ranged from 100-900 abt/km3/hour; in contrast the cumulative flux within the RSZ ranged from 50-550 abt/km3/hour below the RSZ and from 50-500 abt/km3/hour below the RSZ and was <50 abt/km3/hour within the RSZ. At night during spring 2009, the cumulative flux ranges from <25- 1,000 abt/km3/hour and from <25-775 abt/km3/hour. Cumulative diurnal and nocturnal flux in the high altitude band was <5 abt/km3/hour throughout the spring season.

 

Fall 2008

  • Radar data are limited in duration and were insufficient to make any conclusions.

Spring 2008

  • Radar data collection was limited in duration (two days) and data were insufficient to make any conclusions.

Onshore Flux

 

Spring 2008 – Fall 2009

  • Overall, although some flux occurred within the RSZ during the daytime, most bird movements were below the RSZ in 2008 and 2009. At night, when no migration was occurring, the cumulative flux values were greater below the RSZ than within the RSZ. When migration occurred the flux increased within and above the RSZ.

During spring 2008, the cumulative daytime flux ranged from >50-750 abt/km3/hour below the RSZ and from >150-300 abt/km3/hour above the RSZ. In spring during the night, the majority of movement below the RSZ ranged from 100-900 abt/km3/hour; in contrast the cumulative flux within the RSZ ranged from 50-550 abt/km3/hour below the RSZ and from 50-500 abt/km3/hour below the RSZ and was <50 abt/km3/hour within the RSZ. At night during spring 2009, the cumulative flux ranges from <25- 1,000 abt/km3/hour and from <25-775 abt/km3/hour. Cumulative diurnal and nocturnal flux in the high altitude band was <5 abt/km3/hour throughout the spring season.

 

In fall 2008, the cumulative daytime flux ranged from >50-550 abt/km3/hour below the RSZ and from 50-500 abt/km3/hour below the RSZ and was <50 abt/km3/hour within the RSZ. At night during spring 2009, the cumulative flux ranges from <25- 1,000 abt/km3/hour and from <25-775 abt/km3/hour. Cumulative diurnal and nocturnal flux in the high altitude band was <5 abt/km3/hour throughout the spring season.

 

During spring 2009, the cumulative daytime flux ranged from >50-500 abt/km3/hour below the RSZ and was <50 abt/km3/hour within the RSZ. At night during spring 2009, the cumulative flux ranges from <25- 1,000 abt/km3/hour and from <25-775 abt/km3/hour. Cumulative diurnal and nocturnal flux in the high altitude band was <5 abt/km3/hour throughout the spring season.

 

In fall 2009, for most sample dates, the cumulative flux was slightly higher (range: <25-450 abt/km3/hour) below the RSZ than within the RSZ (range: <25-100 abt/km3/hour). This trend also occurred at night, however, the cumulative flux within the RSZ at night (range: <25-900 abt/km3/hour was only slightly below that recorded below the RSZ (range: <25-1,200 abt/km3/hour). Cumulative diurnal and nocturnal flux in the high altitude band was <1 abt/km3/hour throughout the fall season.

 

THERMAL IMAGING-VERTICALLY POINTED RADAR

 

Use of thermal imagery and vertically pointing radar proved to be very valuable in identifying the sources of echoes detected in VerCat. The TI-VPR system could easily detect targets flying through the RSZ. The vertically pointing radar provided accurate altitudes of flight and the thermal imaging video provided enough information on targets to identify them as birds, foraging bats, or insects. Overall, sampling time was limited, especially at onshore sites and offshore sites after spring 2008 because of weather conditions (clouds, rain), and therefore conclusions are limited.

 

General overall conclusions and trends regarding bird flux altitude distribution are presented first and then are followed by a detailed summary of flux abundance within each altitude zone. Overall, sampling time was limited, especially at onshore sites and offshore sites after spring 2008 because of weather conditions (clouds, rain), and therefore conclusions were limited. Comparisons between the avian radar and TI-VPR data were not made because of the lower number of TI-VPR surveys. Overall, the general conclusions were:

  • The majority of birds detected were within the RSZ at the offshore and onshore survey locations during the nighttime sampling periods.
  • More foraging bats were detected in fall and more bats were detected offshore than onshore; bats were detected at distances up to 16.1 kilometers (km; 10 miles [mi]) offshore.

During spring 2008, the majority of bird movements occurred within the RSZ. Bird flight direction was primarily from the north-northwest to the north-northeast. Nine foraging bats were detected at distances up to 16.1 km (10 mi) offshore. In contrast to spring 2008, bird movements below and within the RSZ were nearly equal during fall 2008; however, this result may have been affected by the limited survey time during fall. Flight direction was primarily to the southwest and showed little variability. In contrast to spring, more foraging bats were detected even though the sampling effort was limited.

 

In spring 2009, the mean directions of the movements were towards the northwest-northeast to the north-northeast; one movement was a reverse migration toward the south-southwest. No foraging bats were detected.

 

Offshore

  • During the nights sampled in spring 2008 and 2009, the majority of bird movements (75%) occurred within the RSZ.
  • The majority of birds (50-75%) were detected within the RSZ during fall 2009.

Onshore

  • Most of the birds (90%) detected were flying within the RSZ
  • During spring 2009, all of the detected birds were above the RSZ.
  • The majority of birds (50-75%) were detected within the RSZ during fall 2009 Surveys were limited in fall 2008 to one location and/or by weather conditions (clouds, rain). The majority of the birds were moving to the south-southwest. Flight directions were more variable in fall but generally ranged from the southwest to southeast. Six foraging bats were detected.

 

During limited sampling in spring 2009, all of the detected birds were above the RSZ. Birds were detected moving to the northeast. No foraging bats were detected in spring 2009.

 

The majority of the birds detected were within the RSZ. Flight directions were more variable in fall but generally ranged from the southwest to southeast. Six foraging bats were detected.

 

NEXRAD

 

The overall conclusions of the NEXRAD study were:

  • Nearshore bird densities were higher than offshore bird densities in both spring and fall; overall, the density of migration during the fall was on average two to three times greater than the density of migration observed during the spring.
  • In the spring, the mean directions from which the movements ranges from 203 to 211° and flights were oriented toward the north-northeast (23° to 32°) 17 to 35° and in fall flights were oriented toward the southeast to south-southwest (197 to 214°).
  • Nocturnal migration during the spring and fall shows considerable night-to-night variability. In the spring, migration begins to build in late April, peaks near the middle of May, and then declines towards the end of May. Fall migration builds in early September and peaks in mid-October to early November. After the peak in late October/early November the density of migration declines, and by mid-November very little migratory movement takes place.
  • During the five years of spring data, 79 of 365 nights had conditions that would cause birds to fly lower -- sometimes with reduced visibility. Twenty-nine of these nights had migration densities of 25 birds/km3 or greater.
  • During the five years of fall data, 102 of 465 nights had weather conditions that might cause birds to migrate at low altitudes and 24 of these nights had bird movements of 25 birds/km3 or greater.
  • Over the five fall seasons there were 23 more nights than in five spring seasons with weather conditions that could cause birds to fly at low altitudes and sometimes in poor visibility, but generally on these nights there was little or no migration.

Year-to-Year Pattern of Migration

 

During the spring the sum of nightly peak density (a metric calculated from the summation of the maximum density [birds/km3] recorded for each evening during a season) differed from year-to-year. As expected, the maximum density of migration measured over the coastal sample areas differed from the maximum density over the offshore sample areas. This can be attributed to the bird’s tendency to follow the coast line during their migration. Over the five years of fall data the sum of the nightly peak densities measured over the onshore sample areas ranged from 1,445 (area 3A) in the fall of 2004 to 4,078 (area 1A) in the fall of 2005, with a maximum density of 705 recorded in the fall of 2005 (area 1A). The range of the sum of nightly peak densities over the offshore sample areas ranged from 273 (area 1B) in the fall of 2004 to 658 (area 2B) in the fall of 2005, with a maximum density of 144 recorded in the fall of 2005 (area 2B).

 

Night-to-Night Pattern of Migration

 

Nocturnal migration during the spring and fall shows considerable night-to-night variability. Within the three onshore sample areas there were five nights with a mean density of 100 birds/km3 or greater over the sample areas during the five years of spring migration (21 April, and 01, 04, 07, 11 May), while within the offshore sample areas the maximum was 21 on 21 April [area 1B]). Within the offshore sample areas the mean migration density was considerably less than that measured over the onshore areas (mean peak density of 21 birds/km3). Though sizable flights can occur anytime from the middle of April through the middle of May, the peak of migration through the area is in early to mid-May. Fall migration builds in early September and peaks in mid-October to early November. After the peak in late October/early November the density of migration declines, and by mid-November very little migratory movement takes place. This pattern can be seen both within the onshore sample areas and within the offshore sample areas. There were 17 nights with a mean density of 100 birds/km3 or more within the onshore sample areas during the five years of fall migration (31 August, 01, 10, 13, 15, 23, 26, 29 September and 05, 12, 14, 15, 17, 20, 25 October, and 02, 09 November), while within the offshore sample areas there were zero nights with a mean density of 100 birds/km3 or more. Area 1A measured the highest density for the fall season on 15 October with a mean density of 258 birds/km3. Similar to the spring, the offshore sample area mean migration densities were considerably less than those measured within the onshore sample area. The maximum mean density only measured 34 birds/km3 on 12 September within Area 1B.

 

Direction of Migratory Movements

 

In the spring, there was some variability in mean direction from year to year but within each year there was relatively strong directionality as indicated by the length of the mean vector [r] (a statistical measure of concentration). All yearly mean directions show low circular variance and are highly significant (p<0.000). In the fall, the lengths of the mean vectors from the fall data were comparable to those in spring data. Topographic features such as the shoreline likely influence the directions of seasonal migrations, particularly those occurring at lower altitudes.

 

AVIAN PREDICTIVE MODELING

 

One of the primary goals of the study was to develop spatial models for predicting changes in density and spatial distribution of birds and to identify important regions used by birds within the Study Area. The objective was to quantify where birds are most likely to concentrate in relation to geophysical habitat features (e.g. depth, shoals) and predict where birds were likely to occur seasonally. The following questions were addressed: (1) Where and when are birds (species) most likely to concentrate within the Study Area? (2) Are birds more or less concentrated evenly along the coast, or do some species exhibit specific spatial gradients (i.e. latitude/longitude variation)? (3) What is the relationship between bird density/distribution and depth, distance to shoreline, distance to shoals, and slope?

 

Interpolation (e.g. kernel density), spatial regression, and generalized additive models (GAMs) were used to quantify the relationship between spatial covariates (e.g. bathymetric and distance based metrics) and birds. The spatial models were developed to quantify the effect of each spatial covariate for predicting changes in bird density and distribution. In summary, along with the kernel density maps that identified where and when birds were likely to concentrate, spatial covariates were calculated to develop insight into the geographic distribution and describe the basic attributes of habitat utilized by birds. By incorporating these data in a geographic information system, changes in bird density were determined as a function of depth, slope, distance to shoreline, distance to shoals, and whether there was a spatial gradient in bird density (north/south or east/west) for a variety of species. Collection of kernel density maps was a valuable tool for identifying important locations where and when (by month and season) birds were most likely to concentrate.

 

Kernel Density Interpolation

 

Kernel density maps were estimated for all-behavior and sitting densities (number of birds/km2) in 2008 and 2009, and the combined two-year period 2008-2009. Numerous localized density maxima for all-behavior and sitting birds were located nearshore, midshore, and far-offshore, with the vast majority of these maxima occurring nearshore. A small portion of these density maxima for all-behavior birds are mirrored by the sitting birds, reflecting differences in the numbers of flying and sitting birds. For example, eight and 15 localized sitting density maxima occurred in 2008 and 2009, respectively; and 24 such maxima occurred in the overall cumulative two-year period, most of which occurred nearshore. In 2008, the eight sitting density maxima ranged from 110 to 830 (the latter occurring between Barnegat Light and Seaside Heights and in 2009, the 15 sitting density maxima ranged from 115 to 735 (the latter occurring north of Little Egg Inlet). In the overall cumulative two-year period, the 24 sitting density maxima ranged from 115 to 1,480 (the latter occurring north of Little Egg Inlet). For the all-behavior birds, the highest density maxima were 1,425 in 2008 (midshore southeast of Little Egg Inlet), 1,730 in 2009 (nearshore north of Little Egg Inlet), and 1,805 (on the offshore edge of the nearshore region, between Little Egg Inlet to Brigantine).

 

Observing these annual and overall cumulative spatial kernel density maps, the following general conclusions can be made:

  • Nearshore densities are higher than offshore densities, supporting an offshore gradient of decreasing densities with increasing offshore distance.
  • Within the offshore region, midshore densities were generally higher than far-offshore densities.
  • All-behavior densities were higher than sitting densities, reflecting the presence of both all-behavior and sitting birds.
  • The highest nearshore densities occurred up against the coastline rather than on the offshore edge of the nearshore region.
  • Densities of birds were also higher in shoal areas.

 

Predictive Modeling

 

In general, depth and distance to shoreline were found to be important predictors of bird density and distribution. For example, using the combined two year dataset, it was determined that bird density and distribution declined in waters greater than 20 m (65.6 ft) in depth and 12.2 km (7.6 mi) from the coastline; however, there was a strong seasonal effect in the location of bird aggregations in relation to depth and distance to shoreline. In fall, when bird density was highest (i.e., migration and seasonal visitors take up residence along the New Jersey coastline) birds were concentrated in waters up to 20 m (65.6 ft) in depth and 12.2 km (7.6 mi) from the coastline. In spring, birds were found concentrated in deeper waters (>20 m [65.6 ft) than in the fall (<20 m), and density was lower. In summer, bird density ranged further offshore (18.3 km [11.4 mi]) and increased significantly in waters greater than 30 m (98.4 ft) in depth. In winter, bird density was concentrated in waters less than 15 m (49.2 ft) in depth and within 12.2 km (7.6 mi) from the coastline. Therefore, there is a moderate shift in concentrations of total bird density from close to shore (fall and winter) to offshore (spring and summer) that is attributed to changes in avian community composition.

 

Total sitting bird density was modeled to identify where birds are most likely to reside, concentrate, and for some species, feed (i.e. loons, ducks, and gulls sitting on the water may indicate foraging locations). In general, sitting birds were most likely to occur in waters less than 15 m in depth and within 3.8 mi from the coastline. In fact, in fall, spring, and winter, sitting bird density was concentrated in waters within 6.1 km (3.8 mi) from the coastline, whereas in summer the distance increased to 18.3 km (11.4 mi).

 

The seasonal changes in density and distribution of total birds were dynamic and related to changes in bird community composition. For example, in the fall and winter there were dense concentrations of diving ducks that were absent in the summer when the bird community was primarily composed of terns, gulls and petrels. This difference in community composition was likely responsible for the varying degree of bird density clustered inshore and offshore. The models detected this and quantified habitat use by total birds as a function of depth and distance to shoreline. These dynamics were investigated further to quantify the effect of covariates for predicting changes in species distribution. Scoter density and distribution exhibited a peak in waters 10 m (32.8 ft) in depth and were concentrated within 6.1 km (3.8 mi) from the coast and increased offshore to approximately 30.6 km (19 mi) from the coast. Northern Gannets, which were present in each season, were generally concentrated in waters greater than 10 m (32.8 ft) in depth that was within 25.3 km (9.5 mi) from the coastline. Laughing Gulls and Common Terns, which were seasonal summertime breeders in New Jersey, displayed interesting distribution patterns. Laughing Gulls were generally concentrated within 7.6 km (4.7 mi) from the coast and decreased in waters greater than 15 m in depth. On the other hand, Common Terns ranged further offshore and their density declined around 18.3 km (11.4 mi) from the coast, and thereby occupied a wider range of coastal habitat than Laughing Gulls. The density and distribution of Cory Shearwaters, which were also summertime visitors, showed an increase in density offshore in waters greater than 30 m (98.4 ft) in depth to approximately 27.3 km (17 mi) from the coastline.

 

Overall, bird density and spatial distribution exhibited a striking onshore to offshore gradient that was highly variable among seasons and linked to changes in community composition. The results pinpoints where repeated maximum densities are likely to occur in relation to a variety of species. This information was integral to the understanding of the spatial ecology of marine birds along the New Jersey coastline and should be used to examine potential changes in habitat due to environmental changes from human activity (e.g., offshore wind development, water quality degradation, etc.).

Find Tethys on InstagramFind Tethys on FacebookFind Tethys on Twitter
 
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.