Start at the Delaware Water Gap National Recreation Area Visitor Center at the last exit off Rte. 80 in New Jersey before Pennsylvania. Come under Rte. 80 and park in the visitor center. Scan the ridges for ravens and Black Vulture. Check the trees around the visitor center for both orioles, creeper and Warbling Vireo, and the riverbank for Rough-winged Swallow. Com. Mergansers can be seen in the river; they breed up on the Flatbrook but may be seen anywhere along the river.
After the visitor center, drive under Rte. 80 into the westbound lane again and park in the last parking lot before Old Mine Road at Dunnfield Creek Natural Area. Walk the trail a short distance here up the ravine and check for Worm-eating Warbler on the slope, and along the stream, Louisiana Waterthrush, Solitary Vireo and Acadian Flycatcher as well as other warblers. You could spend all day here, but don't--there's lots more. Proceed from here west on 80 to the last exit again and start going north on Old Mine Road through Worthington State Forest.
Old Mine Road is well known for eagles in the winter, but is less known for its excellent warbler migration and June array of breeding birds. If you hit it about Aril 30-May 1, you can get a good warbler list because warblers seem to hit down in the Delaware Valley a bit sooner than they do in the Highlands or higher in the Kittatinny. But the road is terrific in June for breeding birds such as Cerulean and Hooded warblers, N. Parula, redstarts beyond understanding, Yellow-throated and Warbling vireos, creeper and many other species. As you start up the road, drive slowly, keeping the windows open, and stop wherever there is singing by the target species. In Worthington, pay attention to the Norway spruce groves for parula, areas of dense undergrowth for Hooded Warbler, and big sycamores for Cerulean. Ceruleans can actually be seen on this road, even in June! Tanagers, orioles, Rose-breasted Grosbeak, Wood Thrush, and Veery are all common, and you'll get Chestnut-sided, Pine, Blue-winged and other breeding warblers in the right habitats.
Continuing north, stop at Poxono for a look out on the river for swallows, Spotted Sandpiper, mergansers, flycatchers, etc. Pileated Woodpecker is a possibility anywhere along the route. Also be sure to stop at Depew when you re-enter the National Recreation Area. It has picnic tables and facilities, is a good place for lunch, and has breeding Orchard Oriole, Warbling Vireo, Blue-winged Warbler, Indigo Bunting and hummingbird. For the hummer, check the wires on the road on your way out. There is often a hummer right on the road just above the Depew entrance. They also occur elsewhere on the road, often on the wires.
Moving right along, stop at Van Campen's Glen on the right. Solitary Vireo, Black-throated Green and Blackburnian warblers and Louisiana Waterthrush breed here. After van Campen's Glen, when you come to the pine plantings and overgrown cedar areas, stop for Prairie and Pine Warbler. Then proceed north on Mine Rd. to Watergate. Watergate is a picnic area with a lake and pine plantings, and some different habitat from the rest of the trip. Look here for Purple Finch, creeper, Pine Warbler, Least and Crested flycatchers, Cedar Waxwing and swallows. Cliff swallow has occasionally nested on one of the old structures and roughwing and tree swallows are also here. Both cuckoos have been found here and it is a good place to spot resident raptors up for a soar; any of the 3 accipiters, red-shoulder and redtail can be had if the weather is good.
The Gap to Watergate makes a nice trip. You can go further, all the way up to Dingman's bridge if you like, but you may want to work back along the road to the gap instead, picking up birds that were heard but not seen.