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Thompson's Island
Sussex County, DE

Birding Delaware’s Prehistoric Past:
Thompson's Island at Delaware Seashore State Park
by Andrew P. Ednie


The first sign that a spring fallout had occurred were the three male Bay-breasted Warblers that greeted us at the head of the trail. The early morning sun hitting their throats made their creamy color glow in contrast to the new green in the leaves coming out. Walking into the woods behind Rehoboth Beach, I saw a thrush hopping across the path. Not your typical thrush … this one had an olive green back. I motioned to my birding partner, Ralph Kelly, to hold fast. Ralph was a northern Delaware birder, about to get his first dose of birding coastal Delaware in the spring. First one, then two, then three, then the forest floor was alive with feeding thrushes. We quickly identified American Robin, Wood Thrush, Veery, Swainson’s Thrush, and Gray-Cheeked Thrush. Walking to the edge of the woods, we were greeted by a pair of Eastern Bluebirds by the marsh. This was the first time I had bluebirds in Rehoboth and it brought us to six species of thrush in ten minutes. We might have had more, but Bicknell’s Thrush wasn’t a species then. We ended the walk with over 20 species of warblers. Not bad for about an hour of birding.

Located between Rehoboth and Dewey Beach, Thompson’s Island is part of Delaware Seashore State Park. The island is a 68 acre peninsula jutting out into the north end of Rehoboth Bay. Stockley Creek, which runs into the Head of the Bay at Dewey, dissects the island from the mainland. Thompson’s is not really an island except at storm tides when it is cut off from the mainland. The entire area is only about 120 acres. It is a difficult place to find; there are no parking lots. Access is by foot or boat. The trailhead is located in the Spring Lake condominiums off Delaware Rt. 1, just south of the Lewes-Rehoboth Canal. Turn west at the first light south of the bridge over the canal into the condos. Take the first left hand fork and drive back to the woods. Park by the culvert as the driveway starts to turn left and look for an opening into the woods that is the start of the trail. There is no parking here, there are no trail signs. The area remains undisturbed and wild.

Thompson’s Island became known purely by accident. I was reading Carl Weslager's Delaware’s Buried Past. At that time, Island Fields, the state prehistoric Native American museum, was still open at South Bower's Beach. This inspired me to look for more archeological sites in the state. Professor Weslager mentions an area of high ground behind Rehoboth Beach that was used as a camp site. The Indians (ancestors of the Nanticoke) spent time here to hunt, fish and gather oysters. The trick in finding their campsites is to look for the old fossilized piles of oyster shells. In fact, the Indians threw everything into these piles: trash, dogs, each other, etc. The area was excavated several times from 1960-1990. The remains date from the Woodlawn II period, from 3000 BC to 1600 AD. The natives buried their dead in communal graves, called an ossuary. In April 1983, I went back into the woods at Thompson's Island to look for these pits. What I found was a wonderful birding area, mixed old growth pines and oaks along the coast that has been undisturbed for years. Some of the biggest oaks in Delaware are on the trail to the island. I immediately heard a Yellow-throated Warbler, and lots of Yellow-Rumps, Pines, and Palms were seen. I knew I would be coming back here for the North American Migration Day count.

I heard Paul Lehman talk about looking for migration traps like islands, peninsulas, and oasis. Thompson’s Island is all that. It is the last stand of mature forest left along the Delaware coast, only a half mile from the beach. The peninsula funnels migrants onto the island, where they are trapped by seven miles of inland bays and coast. Birds hitting the coast are attracted to the island as a place to rest, refuel, and seek shelter. The island provides nine different habitat zones from which to choose: wood edge, hardwood swamp, Carolina bay, Virginia Pine woods, brackish marsh, mature mixed hardwood/loblolly forest, salt marsh, pine plantation, and wild cherry orchard. The trick is picking where to spend your birding time in the zones that are the most productive at that time of year.

When you first enter the trail, the Spring Lake roadway runs past a mature woods edge that faces east into the morning sun. This is an excellent area for Neotropical migrants catching insects at first light. Yellow-billed Cuckoo, Eastern Wood Pewee, Blue-headed Vireo, Nashville Warbler and Rose-breasted Grosbeak are frequently found. The trail is 1.5 miles out to Thompson’s Island, running through woods, marsh, and along the canal. As you enter into the woods, the first zone is swamp maples, good habitat for Hooded Warbler and Acadian Flycatcher. Associated with the Swamp Maple is a unique Delmarva feature, the Carolina Bay. Also called “whale wallows”, these sinkhole depressions were once thought to be caused in the ancient sea floor by prehistoric whales. During wet springs, water collects here to provide habitat for Northern Waterthrush. Alongside the Carolina bay is a stand of Virginia Pines, giving the area that southern feeling found in “slower” Delaware. Scarlet and rarely Summer Tanagers are found among the pines. The forest floor is open, providing habitat for pluming Pink Lady Slippers. It is also a favorite area for thrushes, as previously described.

As you leave this area of forest, the first obstacle of the trail is a brackish marsh. A small creek runs through the marsh, entering the Rehoboth-Lewes Canal to the north just behind the Rehoboth Beach water treatment plant. At spring tides, several feet of water will back up into the marsh. A good pair of boots may be needed to wade through. Lately, a wooden pier has been anchored over the creek to allow access. The marsh has produced some outstanding finds, such as Sedge Wren and King Rail. In the fall, it is a favorite open area to watch Merlins zipping through, taking dragonflies or swallows. At the far edge of the marsh is a Division of Fish and Wildlife sign, announcing that you are entering Thompson’s Island. This is the only clue that you are at the right place.

The woods after the marsh is one of the oldest, most mature woods in Delaware. The dominate species are White Oak and Loblolly Pine. Since Loblolly is the dominate wood for lumbering, it is surprising to see 100 year old trees still standing. As you walk down the trail, the forest canopy becomes dominated by a single White Oak. This tree is 80-100 feet tall, with a girth of 36 inches. It is easily 250 years old. Warblers can be found in abundance when this tree flowers in spring. Even at the canopy’s great height, the orange of a Blackburnian Warbler’s throat appears incandescent in the morning light. A cacophony of sound is produced from the singing Pine Warblers, Northern Parulas, and Red-eyed Vireos.

Further along, you begin to leave the woods at the edge of the Lewes-Rehoboth Canal. The salt marsh from Stockley Creek is to the east, while the Bay Vista marsh is across the canal. Seaside Sparrows sing from the sedges and Tricolored Herons can be seen feeding in the marsh. Salt Marsh Sharp-tailed Sparrows can be found in the Bay Vista marsh and it is the last place that Henslow’s Sparrow was reported in Delaware. Walking through the marsh, the trail is constructed from the dike along the canal. This opening provides a panorama, allowing birders to scan for perched Bald Eagles in the dead pines along the marsh edges.

Finally, after a half hour hike, you are actually on the island. The park requires that you stay on the path, not entering the center of the island. That is where the archeological deposits and grave sites are located. Due to the sensitive nature of the Native American religious philosophy, this area is off limits. The center of Thompson’s Island was cultivated and used as pasture land until the end of the 19th century. A second growth woods is in the middle of the island which isn’t very productive for birding. Immediately, the trail enters the edge of an old White Pine plantation. This area seems to attract Blackpoll and Worm-eating Warblers. The trail ends at the north end of Rehoboth Bay at the mouth of the canal. A pair of jetties guards the mouth, providing perches for Black Skimmer and American Oystercatcher. One of Delaware’s best kept secrets is that hundreds of Horned Grebes stage for migration at the north end of Rehoboth Bay. Sometimes there are rafts of over a hundred birds sitting and feeding off the island. Every year in early March, an Eared Grebe is found here at the Head of the Bay. If you take the trail completely around the island, you’ll pass by the bluffs over the bay, where erosion exposes the fossilized oyster shell piles. The woods are an old orchard now filled with chokecherry. These woods attract Blue Grosbeak and cuckoos drawn to the insects and tent caterpillars. The trail doubles back and meets at the pine plantation to head back to Spring Lake.

There are dangers when birding the island. Nobody birds Thompson’s Island during the summer, unless they want to be at the mercy of the dreaded Greenhead Flies. “Fly season” starts in early June and can extend into September. Fall birding is excellent for passerines, but you have to stay on the trails. Chiggers in the autumn are prevalent, leaving several weeks of itchy welts on the skin. During the winter, hunters use the island for deer and waterfowl. Hunters desecrating the Native American burial site caused the state to close the island to all visitors from 1995-2000. Hunting has since been banned, creating an overpopulation of deer. Spring is tick season. The large herd of White-tailed Deer has created a huge population of the Black-legged or Deer tick, a vector for Lyme disease. Dog and Lone-star Ticks are also common, and are vectors for other pathogens. In 2003, I contracted ehrlichiosis after a tick bite received on Thompson’s Island. Ten days later, high fevers started that persisted for two weeks. Luckily, quick treatment with Doxycycline prevented hospitalization.

Most birders visit Thompson’s Island because Brown-headed Nuthatches are residents. Other residents such as Hairy Woodpecker and Belted Kingfisher, which are hard to find along the coast, can be found. The pond at Spring Lake produces interesting waterfowl; Canvasback, Redhead, and even Tufted Duck. Field birds like Horned Lark, Snow Bunting, and Water Pipit are the only species missing from the area. Two factors influence birding, seasons and weather. If the oaks are in bloom, watch for warblers. If the oaks are past, move to the later blooming cherry trees. Watch the weather, the best time is before a frontline, with a southwest wind followed by a raising warm front during the night. That will push migrants in and ground them. An east wind pushes migrants inland, killing birding on the island. Like Cape May’s Higbee Beach, the island is a migration trap. Personally, I’ve recorded 205 species on the island, which I only get to visit a couple times a year. Included in that total are six species of vireo and 36 species of warbler. That is every species of commonly occurring warbler found in Delaware. Maybe, someday a Swainson’s Warbler will be there. Hopefully, I’ll be visiting too.