Baldpate Mountain Important Bird Area (IBA)

Baldpate Mountain is a very special place

Surrounded by a biological desert, Baldpate Mountain is a hotspot of biodiversity. Baldpate is part of the Greater Sourland Mountain Ecosystem, a high area formed by erosion resistant diabase after the softer surrounding rocks eroded away. As a raised wetland with poor drainage, this ecosystem has resisted development, leaving the two largest contiguous forested areas in central New Jersey. Because of its steep slopes and history of deer hunting, Baldpate Mountain has retained the greatest expanse of healthy understory in the Greater Sourland Ecosystem. The Sourland Mountain has a greater area of contiguous forest, but Baldpate has a larger expanse of high quality understory with four areas of extensive understory dominated by native plants, primarily Spicebush.

Because of the combination of contiguous forest, high quality understory, and its location as the meeting place of Southern and Northern species, Baldpate Mountain has the highest concentration of nesting Nearctic-neotropical birds in New Jersey and the largest number of species of breeding Nearctic-neotropical migrants in central New Jersey. The interior forest has breeding Cerulean Warblers, Hooded Warblers, Kentucky Warblers, and Worm-eating Warblers, Wood Thrush and Veery, all New Jersey species of conservation concern. The forest has a mosaic of habitats, with naturally occurring treefall gaps supporting a tangle of vegetation that supports a different group of species, including the American Redstart. Baldpate also supports edge breeding species, especially where there is a soft edge between the forest and the open areas, giving a total of thirteen breeding wood warblers, which makes Baldpate a birding mecca. The area attracts large numbers of species of migrating Nearctic-Neotropical migrants, as well. Several New Jersey threatened raptors, including Barred and Long-eared Owls and Red-shouldered Hawks, use Baldpate for at least part of their life-cycle. Cooper’s Hawks, a New Jersey species of conservation concern, breed at Baldpate.

WCAS has been monitoring bird populations at Baldpate since 2000 and conducted two breeding studies. NJ state threatened Long-eared Owl roosts in Baldpate’s dense evergreens.
Long-eared Owl NJ State Threatened © Sharyn Magee
Healthy spicebush understory (below) at Baldpate provides dense nest cover in Spring. Central and South America bound migrants fatten up on its lipid-rich red berries in Fall.
Healthy spicebush understory at Baldpate © Sharyn Magee
Baldpate is Mercer County’s highest mountain with views of the Delaware River, Trenton and Philadelphia.

Baldpate Mountain Trail Map PDF

Over 12 miles of trails meander through 1,500 mostly forested acres, diabase boulders, and historic ruins
‘Devil’s in the diabase’—Baldpate is part of the Greater Sourland Mountain Ecosystem, a high area formed by erosion resistant diabase after the softer surrounding rocks eroded away. As a raised wetland with poor drainage, this ecosystem has resisted development, leaving the two largest contiguous forested areas in central New Jersey. Diabase weathers into mineral rich clay soils that support distinct, uncommon plant communities.

Baldpate Mountain was designated as an Important Bird Area due to all these factors. For an area to support this number of birds, it must support an intact ecosystem with other taxa, especially native plants and insects, having healthy populations and diversity. In addition to rare birds, Baldpate supports rare reptiles, including NJ species of special concern Eastern Box Turtle and Agkistrodon contortrix and rare amphibians, including the Fowler’s Toad and Spotted Salamander.

While Baldpate has an intact ecosystem, it is also highly stressed. Baldpate is at the lower size limit for an interior forest habitat and its shape is long and narrow, increasing its vulnerability to edge effect. Increased edge effect increases the number of invasive species, especially non-native plants, and the Brown-headed Cowbird, a nest parasite. Any reduction in size of Baldpate would have serious consequences, both by threatening native plants and increasing the incidence of Brownheaded Cowbird nest predation. Nest predators, such as the Eastern Chipmunk, which have higher concentrations on the edges and in disturbed areas, would thrive. The proposed PennEast pipeline runs along the north slope of the mountain and would change one of the high quality interior forest habitats into edge habitat and bring the edge closer to the other areas of high quality habitat, seriously degrading an already stressed ecosystem.

Long-spurred Violet (Viola rostrata) NJ Species of Concern © Tyler Christensen
Healthy bird populations indicate healthy, diverse populations of other taxa, notably the plants and insects upon which the birds depend. Above: rare Long-spurred violet (Viola rostrata) © Tyler Christensen; right: Dutchman’s breeches (Dicentra cucullaria); other wildflowers © Fairfax Hutter; top: hiker © Pat Sziber; spicebush & all bird photos this page © Sharyn Magee unless otherwise noted.

30 of the 31 Nearctic-neotropical migrants including 14 Warblers who breed at Baldpate

Four of the 90 Nearctic-neotropical migrants who use Baldpate as critical stop over habitat

Baldpate’s Wintering Residents and Winter Migrants

Baldpate’s Year Round Residents

Red-shouldered Hawk
Yellow-billed Cuckoo
Black-billed Cuckoo
Common Nighthawk
Barred Owl
Long-eared Owl
Eastern Screech Owl
Chimney Swift
Belted Kingfisher
Red-headed Woodpecker
Northern Flicker
Olive-sided Flycatcher
Eastern-wood Peewee
Acadian Flycatcher
Yellow-throated Vireo
Blue-headed Vireo

Warbling Vireo
Philadelphia Vireo
Northern Rough-winged Swallow
Carolina Chickadee
Veery
Gray-cheeked Thrush
Swainson’s Thrush
Wood Thrush
Brown Thrasher
Cerulean Warbler
Ovenbird
Worm-eating Warbler
Louisiana Waterthrush
Northern Waterthrush
Blue-winged Warbler

Golden-winged Warbler
Black-and-white Warbler
Prothonotary Warbler
Tennessee Warbler
Nashville Warbler
Connecticut Warbler
Mourning Warbler
Kentucky Warbler
Common Yellowthroat
Hooded Warbler
American Redstart
Cape May Warbler
Northern Parula
Blackburnian Warbler
Chestnut-sided Warbler
Bay-breasted Warbler
Blackpoll Warbler

Black-throated blue Warbler
Yellow-throated Warbler
Prairie Warbler
Black-throated Green Warbler
Canada Warbler
Wilson’s Warbler
Yellow-breasted Chat
Eastern Towhee
Summer Tanager
Scarlet Tanager
Rose-breasted Grosbeak
Indigo Bunting
Baltimore Oriole