Keystone Park has often been called a gem and it is. But that description does not pay it justice. It is simply hard to throw enough superlatives at this little-known park. Keystone Park lies in a bend of the South River and features an interesting but small forest of mature trees, a few trails, a large freshwater tidal marsh and a maintained lawn\field, perfect for a secluded picnic or Frisbee toss. The trails are limited to the forest and are fine for a short leisurely stroll, but it is the tidal marsh that beckons the adventurous. Large mature sycamores with their peeling white and green bark stand out in the forest among the oaks that dominate the canopy and are worth a bit of bushwhacking to get right up to them. Bird life in the forest can also be interesting especially when time is limited. A short late winter walk found red-bellied woodpecker, downy woodpecker, chickadee, tufted titmouse, junco, Ruby crowned and Golden crowned kinglets, white-throated sparrow, white-breasted nuthatch and blue jay in just a few minutes. A dense thicket of silky dogwood, catbriar, arrowwood and Japanese honeysuckle forms the interface between the uplands and the marsh and can be very productive for sparrows especially in fall and winter. Given the park’s location along the South River, the large oaks in the forest may also be interesting during the spring migration for warblers and other songbirds. Despite the difficulties of crossing the tidal streams and muck, once the South River is reached at low tide, the banks are firm enough to walk along the entire edge of the river.
But, it is the tidal marsh at Keystone Park that makes this park a haven for the adventurous. There are no trails in the marsh making exploration of this area a challenge (but one that is well worth the effort). The marsh is a large freshwater tidal system flowed by the tides but far enough upstream on the South River to be freshwater. The marsh is crisscrossed by large and small tidal streams and rivulets.
At high tide these are not crossable but at low tide the smaller ones can sometimes be crossed with carefully selected steps or a small jump. Like all tidal marshes, boot-sucking muck prevails in many places and one wrong step can lead to a trip back to the car without footwear or with very wet and muddy apparel. Conferring with a tide table before heading out is warranted (http://www.saltwatertides.com). Timing a visit to insure getting out and back before hide tide rolls in is necessary. The South River is also a prime spot for canoeing and kayaking but access is limited. Nonetheless, this would be an excellent way to explore the waterway and the adjacent marsh.
Wildlife of the marsh and river are abundant and worthy of hours of exploration at all seasons. This may very well be the most reliable place in town to see a bald eagle and is definitely the best place to find nesting marsh wrens in the summer. Walking the marsh in the winter can also yield the distinctive and interesting ball-shaped nest of the marsh wren that is typically suspended in cattails and has a side entrance hole and that can be maddeningly difficult to find in the summer.
The marsh at Keystone Park has been designated a New Jersey Natural Heritage Priority Site by the NJDEP as a prime example of a tidal freshwater ecosystem and because the State-Endangered plant Eaton’s Sticktights (Bidens eatonii) occurs somewhere in the marsh. This is believed to be the only place in New Jersey where this Globally-Rare yellow-flowering plant occurs. The marsh is a mosaic of wetland plants including broad expanses of cattail and the highly aromatic sweetflag.
Scattered buttonbush and the beautiful swamp mallow also occur along with many other wetland plants typical of tidal freshwater marshes. Botanical forays are sure to yield some interesting finds in a rather uncommon wetland habitat type.
A forested wetland “island” in the middle of the marsh has large black gum trees and is well worth trying to get to, if for no other reason then to reach it.
Raptors can also be common including osprey, red tailed hawk, Coopers hawk and Sharp shinned hawk, the latter two especially in migration in the fall. Ducks, herons and other wading birds can also be abundant including Great blue heron, Common egret, black duck, mallard, Canada goose, various peeps, Yellow-legs and snipe among an expected list that will be quite large with exploration over the seasons. An osprey nest platform built by a Boy Scout as his Eagle Scout project remains unused so far but is often a favored perching spot for red tailed hawk.