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.
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.
Baldpate is Mercer County’s highest mountain with views of the Delaware River, Trenton and Philadelphia.
‘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.
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.
31 of the 32 Nearctic-neotropical migrants including 15 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
Birds reported to Baldpate “Hot Spot” on e-Bird
American Black Duck
Great Blue Heron
Great Horned Owl
Northern Saw-whet Owl
Great Crested Flycatcher
Northern Rough-winged Swallow
Carolina x Black-capped Chickadee (hybrid)
Brewster’s Warbler (hybrid)
Cape May Warbler
Black-throated Blue Warbler
Black-throated Green Warbler
American Tree Sparrow