Spatial Distribution, Abundance and Flight Ecology of Birds in Nearshore and Offshore Waters in Rhode Island


Title: Spatial Distribution, Abundance and Flight Ecology of Birds in Nearshore and Offshore Waters in Rhode Island
Publication Date:
June 17, 2010
Document Number: 11
Pages: 304

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Paton, P.; Winiarski, K.; Trocki, C.; McWilliams, S. (2010). Spatial Distribution, Abundance and Flight Ecology of Birds in Nearshore and Offshore Waters in Rhode Island. Report by University of Rhode Island. pp 304.

This interim report for the Rhode Island Special Area Management Plan (SAMP) summarizes our research conducted from January 2009 through mid-February 2010. This research is the first attempt to quantify the spatial distribution and abundance of birds using the nearshore and offshore waters of Rhode Island. Avian research is still ongoing, with ship-based line transect surveys and land-based seawatches continuing from Feb through July 2010. In addition, aerial surveys are planned to continue from Feb 2010 through May 2011. Results from this ongoing research will be presented in another technical report in 2011.


Our objectives for avian research as part of the Ocean Special Area Management Plan (SAMP) were to: (1) Summarize historical studies of avian use of nearshore and offshore waters within Ocean SAMP study area boundaries, (2) Assess seasonal variation in the spatial distribution and abundance of birds in RI nearshore and coastal waters, (3) Assess diel patterns of avian use of RI nearshore and offshore waters, (4) Quantify flight ecology for birds in RI nearshore and offshore waters, and (5) Investigate Roseate Tern use of the Ocean SAMP study area.


The Ocean SAMP study area encompasses 3,800 km2 (about 1,500 miles2) that includes Block Island Sound, Rhode Island Sound, and the Inner Continental Shelf. One of the primary factors determining the spatial distribution and abundance of birds using nearshore and offshore areas is bathymetry. Water depths in the Ocean SAMP study area are relatively deep compared to adjacent areas and average 35 m ± 10 m deep, with 8% of the SAMP area <20 m deep and 86% of the area between 20-50 m deep.


Prior to the current Ocean SAMP avian study, only two systematic surveys of offshore avian communities had been conducted within the Ocean SAMP area. First, avian observers stationed on National Marine Fisheries Service (NMFS) and Coast Guard vessels in 1978-79 detected 4,532 birds in 665 different flocks and 21 bird species. Gulls [38% of detections], shearwaters [26%], and storm-petrels [13%] dominated NMFS surveys. Second, the largest historical offshore survey was the Cetacean and Seabird Assessment Program (CSAP) conducted from 1980 to 1988. CSAP surveyed 101 15-min transects throughout the year using Manomet Bird Observatory observers stationed on vessels conducting plankton, groundfish, and shellfish surveys. CSAP surveys detected 34 species of birds from a total of 14,045 detections, with gulls (69% of detections), shearwaters (16% of detections), and storm-petrels (6% of detections) dominating counts. However, data were too sparse to map the historical spatial distribution and density of birds in the Ocean SAMP study area.


Much more historical information about avian use of nearshore habitats of Narragansett Bay, coastal promontories and peninsulas, and coastal ponds is available from surveys conducted by DEM biologists, volunteers coordinated by EPA, and biologists from US Fish and Wildlife Service’s Rhode Island National Wildlife Refuge complex. Narragansett Bay is home to thousands of wintering waterfowl, with an average of 21,256 ± 12,051 (SD) individuals counted annually, with a maximum of 58,706 individuals in 2001. The most abundant species in the Narragansett Bay based on DEM aerial surveys over the past 27 years included scaup (mean = 6,600 individuals ± 5100 (SD) annually), Canada Geese, (6,300 ± 5400), American Black Duck (2,200 ± 1200), and Common Eider (1250 ± 3000).


Exposed promontories along the coast, such as Sachuest Point NWR, were surveyed by USFWS biologists in the winters from 1992-2003. These areas were dominated by seaducks including Common Eider (560 ± 880 annually), Surf Scoter (110 ± 130), Harlequin Ducks (80 ± 16), and Common Goldeneye (90 ± 30). Surveys conducted throughout the year by DEM biologist C. Raithel at Napatree from 1982 to the present provide valuable information on migration phenology and relative abundance of birds in the northwest corner of the Ocean SAMP area.


Coastal ponds, such as Trustom and Ninigret NWR, have been surveyed during winter by USFWS biologists since 1992. The abundance of dabbling ducks (e.g., American Black Duck, Mallard, American Wigeon, Green-winged Teal and Gadwall) and diving ducks (Greater and Lesser Scaup, Canvasback, Ring-necked Duck and Ruddy Duck) in these coastal ponds demonstrate the value of these habitats for wintering waterfowl.


We used five primary survey methods to assess avian use of the Ocean SAMP area: (1) six 1-2 hr land-based seawatches (≤ 3 km from shore) per month at 11 stations along coastal mainland Rhode Island from 23 Jan 2009 to mid-Feb 2010; (2) systematic ship-based line-transect surveys approximately once a month from February to May 2009 on two 4 by 5 nm grids and then approximately four times per month from June 2009 until March 2010 on eight 4 by 5 nm grids; (3) aerial strip-transect surveys (24 transects, 3 km apart) flown from November 2009 to March 2010 at a fixed altitude of 152 m and at a constant speed of 160 km/hr; (4) boat-based line transect surveys in nearshore waters in the NW corner of the Ocean SAMP area conducted during July and August 2009 to assess the distribution and abundance of Roseate Terns; and (5) a study by ornithologists from New Jersey Audubon Society using both a dual horizontial and vertical radar unit on Block Island to monitor the movement ecology of birds from March to mid-December 2009, 24 hrs per day, 7 days per week (see Appendix K).


We conducted 796 1-2 hr land-based seawatches during this 13-month period. We had 465,039 detections of 121 species during land-based seawatches. The most commonly detected species were scoters, eiders, Herring Gulls, and Great Black-backed Gulls (all scientific names are given in Appendix A). From these data, we were able to assess spatial variation the relative abundance of birds and to model the phenology of common waterbirds using the Ocean SAMP study area.


We conducted 54 ship-based line transect surveys of 8 grids on 27 days between 10 June 2009 and 13 February 2010. We detected 56 species during these surveys, of which 11 species were relatively common: Herring Gull, Wilson’s Storm-Petrel, Northern Gannet, Great Black-backed Gull, Cory’s Shearwater, Common Loon, Greater Shearwater, Black-legged Kittiwake, Razorbill, Common Murre, and Dovekie. Using program DISTANCE, we estimated the seasonal change in the spatial distribution and density of these common species.


We conducted 10 aerial surveys between 18 November 2009 and 22 February 2010. During aerial surveys, we had 9,414 detections of 17 species or guilds, of which the following were most common: Common Eider, unidentified gulls, Northern Gannet, Herring Gulls, unidentified scoters, Common Loon, and unidentified alcids. We compared these data to the spatial distribution and density estimates for common species from the ship-based line transect surveys and developed bathymetry profiles for select species.


We had 125 Roseate Tern detections during land-based point counts, with most detections at the NW corner of the Ocean SAMP study area. We had 8 Roseate Tern detections on 3 ship-based line transect grids in Block Island Sound, but we did not detected Roseate Terns in Rhode Island Sound or the Inner Continental Shelf during ship-based surveys.

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