Northeast Coastal Areas Study
Significant Coastal Habitats
Site 20 (CT)
I. SITE NAME: Norwalk Islands and Tidal Wetlands Complex
II. LOCATION: The Norwalk Islands are located in western Long Island Sound, approximately one to one-and-a-half miles (2 km) offshore (south) of the city of Norwalk, along the southwest coast of Connecticut. The mainland portion of this complex occurs between Rowayton and Sherwood Island State Park.
TOWNS: Norwalk, Westport
USGS 7.5 MIN QUADS: Sherwood Point, Conn-NY 41073-13; Norwalk South, Conn 41073-14; Westport, Conn 41073-23; Norwalk North, Conn 41073-24
USGS 30x60 MIN QUAD: Bridgeport 41073-A1
III. GENERAL BOUNDARY: This complex includes all of the Norwalk Islands (Sheffield Island, Shea Island, Copps Island, Chimon Island, Betts Island, Long Beach Island, Grassy Island, Goose Island, Cockenoe Island and several smaller islands) and the mainland tidal wetlands and mudflats at Fivemile River, Village Creek (Hoyt Island), Norwalk Harbor (Harborview and Seaview Park), Shorehaven-Canfield Island, mouth of Saugatuck River, Compo Cove and Sherwood Millpond, as well as the intervening embayed waters of Long Island Sound. The length of this complex in a southwest-northeast direction is approximately 6 miles (16 km), and 2 to 3 miles (3-5 km) in width. Also included in this complex are the mainstem channels of the Norwalk River up to the vicinity of the Silvermine River, and the Saugatuck River to its confluence with the Aspetuck River, near Sipperly Hill.
IV. OWNERSHIP/PROTECTED STATUS: Most of the larger islands are publicly-owned (Federal National Wildlife Refuge, Town), while many of the smaller ones are in private ownership. The waters and mudflats along the mainland are in the Public Trust (below mean high water). A few of the mainland wetland areas are privately-owned. Many of the larger islands are designated under the Coastal Barriers Resource Act.
V. GENERAL HABITAT DESCRIPTION: The Norwalk Islands are glacial till islands vegetated with varying amounts of coastal woodlands and dense shrub thickets dominated by black cherry (Prunus serotina), sassafras (Sassafras albidum), juniper (Juniperus virginiana), blackberry (Rubus allegheniensis), Asiatic bittersweet (Celastrus orbiculatus), Japanese honeysuckle (Lonicera japonica), poison ivy (Toxicodendron radicans), staghorn sumac (Rhus typhina) and winged sumac (R. copallina), with some open fields of switchgrass (Panicum virgatum) and other grasses. These islands have extensive gravelly, cobbly or rocky beaches, with Russian thistle (Salsola kali var. tenuifolia), sea-beach sandwort (Arenaria peploides) and seaside goldenrod (Solidago sempervirens). There are also offshore tidal mud flats, and some areas of tidal marsh with saltmarsh cordgrass (Spartina alterniflora), saltmeadow cordgrass (S. patens), spike grass (Distichlis spicata) and black grass (Juncus gerardii), similar to what also occurs on the mainland marshes. The mainland coves and harbors contain varying proportions of open shallow water, intertidal mudflats and estuarine low and high saltmarshes. The intertidal flats often have abundant seaweed beds of sea lettuce (Ulva lactuca) in addition to bare, exposed mud. Mean tidal range in this area is 7.2 feet (2.2 m).
VI. SIGNIFICANCE/UNIQUENESS OF AREA: The Norwalk Islands are of high regional significance to breeding colonial wading birds. These rookeries are mostly dominated by black-crowned night-heron (Nycticorax nycticorax), but also include great egret (Casmerodius albus), snowy egret (Egretta thula), cattle egret (Bubulcus ibis), little blue heron (Egretta caerulea), yellow-crowned night-heron (Nyctanassa violacea), green-backed heron (Butorides striatus) and glossy ibis (Plegadis falcinellus). The largest colony--numbering over 1000 pairs comprised of eight species--occurs on Chimon Island and tends to move out and utilize the other islands and mainland marshes and intertidal flats for feeding. The most important wading bird feeding areas in this complex are the tidal flats around some of the islands and on the mainland at Village Creek-Hoyt Island, Norwalk Harbor, Shorehaven-Canfield Island, Saugatuck River mouth and Compo Cove-Sherwood Millpond. Birds from these islands also utilize the mudflats at Great Meadows (Stratford) for feeding. Small nesting colonies of herons and egrets occur on Shea and Grassy Islands and others. Also nesting on beaches on a few of the Norwalk Islands are piping plover (Charadrius melodus), a U.S. Threatened species, least tern (Sterna antillarum), common tern (S. hirundo), and American oystercatcher (Haematopus palliatus). Problem species also nesting in this area include large numbers of great black-backed gulls (Larus marinus) and herring gulls (L. argentatus) and increasing numbers of double-crested cormorant (Phalacrocorax auritus). Roseate tern (Sterna dougallii), a U.S. Endangered species, historically nested on Goose Island. Both the waters and tidal flats around these islands as well as the mainland marsh and cove sites, particularly Fivemile River, Village Creek, Norwalk Harbor, Canfield Island and the mouth of the Saugatuck River, are significant concentration areas for wintering waterfowl of special emphasis, especially American black duck (Anas rubripes), American wigeon (Anas americana), Atlantic brant (Branta bernicla), greater and lesser scaup (Aythya marila and A. affinis, respectively) and gadwall (Anas strepera), as well as many species of shorebirds. Northern diamondback terrapins (Malaclemys t. terrapin) inhabit both island and mainland marshes and adjacent waters. Important American oyster (Crassostrea virginica) and hard-shelled clam (Mercenaria mercenaria) beds occur offshore. The lower reaches of the Norwalk and Saugatuck Rivers have important anadromous fish runs for sea-run brown trout (Salmo trutta), alewife (Alosa pseudoharengus), blueback herring (Alosa aestivalis), rainbow smelt (Osmerus mordax) and white perch (Morone americana).
VII. THREATS: Although most of the Norwalk Islands are already in public ownership and are not likely to be developed, they are still subject to varying degrees of human disturbance, especially to the wading bird rookeries and nesting colonies of beach-nesting piping plovers and terns. Human disturbances in the form of intrusions into nesting areas during the critical nesting and fledging season can cause colonies to be temporarily or even permanently abandoned. Predation of eggs and young birds by Norway rats (Rattus norvegicus) and gulls are also a potential threat to these colonies. The heavily urbanized mainland shoreline in this area poses threats to water quality through chemical contamination, oil spills, sewage and stormwater discharges, waste disposal, marina development, dredging and numerous other activities that potentially degrade both terrestrial and aquatic habitats of fish and wildlife resources. The waters of western Long Island Sound are subject to low oxygen levels (hypoxia) during the summer months which can stress and even kill marine organisms if prolonged.
VIII. CONSERVATION CONSIDERATIONS: The protection and management of colonial wading bird rookeries and colonies of beach-nesting terns and piping plover need to be given high priority in this area. Because these birds are very sensitive and vulnerable to human disturbances during the critical nesting season (mid-April to August), protective strategies and measures should be designed to prevent people and unleashed pets from entering these areas, using such measures as closed areas with fenced exclosures, posting, warden patrols, trapping and removal of pets or feral animals, rats, etc., and public education. Efforts should be made to identify and implement objectives and tasks outlined in the piping plover recovery plan that could be applied to beaches in this area, including enhancement and restoration. Development of a basinwide colonial wading bird conservation and management plan and guidelines should be considered at least for western Long Island Sound and The Narrows, and perhaps also one for wintering waterfowl. Plans should be developed and implemented to control expanding gull populations and exotic vegetation on these nesting islands. Incorporating Shea Island and Grassy Island, as well as Great Meadows, into the Stewart B. McKinney National Wildlife Refuge would allow the Service to protect, restore and manage wildlife habitat of importance to breeding and overwintering birds, and to manage the Norwalk Islands and mainland feeding areas and their living resources as a more complete ecological unit. This area, in addition to Great Meadows Marsh and Menunketesuck Marsh and Island, were the subjects of a November 1989 Environmental Assessment by the Service on proposed additions to the Stewart B. McKinney and Salt Meadow National Wildlife Refuges. Other, privately-owned, areas could provide opportunities for the development and implementation of various land protection mechanisms, including cooperative conservation and management agreements, zoning and land-use regulations and their strict enforcement, conservation easements, land exchanges, and other options.
Protective measures need to be taken, whether by regulation, zoning, planning, cooperative agreements or full-scale restoration programs such as the National Estuary Program, to restore, maintain, enhance and protect the aquatic, terrestrial, insular and benthic habitats of this area to ensure that these areas continue to support the regionally significant populations of waterfowl and colonial breeding birds that utilize and depend upon these habitats. Programs such as the Long Island Sound Study should continue to focus upon solutions to the problem of hypoxia, contaminants and waste disposal in western Long Island Sound.
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