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Important Bird and Birding Areas
Giant Fen Area

IBBA Site Guide

18
Sussex County
Coordinates: N 41.12646
W 74.63782
Skylands: Appalachian Mountains

Area: 21,664 Acres     

Habitat: Nontidal wetlands with upland deciduous and coniferous forest, scrub-shrub and grassland

Site Description: The Giant Fen Area IBA, or the Monroe Big Springs Natural Heritage Priority Site, is a limestone fen wetland complex located in the headwaters of a tributary to the Wallkill River. A limestone fen is a rare ecosystem with mineral rich wetlands usually associated with limestone bedrock. The Giant Fen Area occurs within New Jersey’s “limestone belt” of Sussex and Warren County and is considered the largest of its kind in NJ. The site includes forested wetlands, scrub-shrub and herb dominated meadows. Upland deciduous and coniferous forests buffer the sensitive wetlands from adjacent agriculture and development. This site is located within the Highlands Preservation Area, a region of exceptional natural resource value designated by NJ Department of Environmental Protection’s Highlands Water Protection and Planning Act (Highlands Act). This act was created to preserve open space and protect NJ’s diversity of natural resources.

IBA Criteria:
CriterionSpecies
Conservation Concern – State-endangered (B)American Bittern, Sedge Wren
Conservation Concern – State-threatened (B)King Rail
Regional Responsibility Species - BCR 28 Forest (B)Baltimore Oriole, Eastern Wood-Pewee, Gray Catbird, Scarlet Tanager, Wood Thrush
Sedge Wren
Sedge WrenMichael O'Brien
 
Birds: The freshwater wetlands of Giant Fen Area provide valuable breeding habitat for state-endangered American Bitterns and state-threatened King Rails and Least Bitterns. This site also supports breeding state-endangered Sedge Wrens, state-threatened American Kestrels and Barred Owls and American Woodcocks, a conservation priority species. Short-eared Owls and Northern Harriers utilize this site during the winter.

Conservation: Agricultural and residential development pressure, natural succession and invasive plant species are the greatest threats to this site. Nonpoint source pollution from adjacent agricultural and residential lands can degrade and dilute the mineral rich waters of the limestone fen. Nearby developments should consider their proximity to this wetland and the potential for altering water quality both above and below ground. Development also facilitates invasion by nonnative invasive plants, including purple loosestrife (Lythrum salicaria) and common reed (Phragmites australis), which reduce habitat structure and outcompete native fen species. The Giant Fen Area is also becoming overgrown with trees and shrubs as it naturally succeeds to a forested community. These wetlands require periodic disturbance in the form of grazing, flooding, fire or clearing. Management recommendations include selective cutting of woody species followed by herbicide application to prevent re-growth. In addition, terrestrial buffers should be maintained to filter water flowing into the wetland and provide nesting and foraging habitat for wildlife. Privately-owned portions of this rare, sensitive limestone fen community should also be prioritized for acquisition and habitat restoration. Additional threats include overabundant deer and cowbird parasitism. Overabundant deer reduce habitat structure by browsing heavily on native plants and cowbirds parasitize nests of other birds, ultimately compromising the parents’ ability to raise their own chicks.

Additional Information: Site Report
Inundated fen habitat
Inundated fen habitatJohn Parke