Here’s a short preview of some of the finds you can expect during an outing in the Lower Susquehanna River Watershed’s forests this week…
The Mountain Laurel, designated as Pennsylvania’s state flower, is now in bloom.The buds of the Mountain Laurel remind us of a sugary frosting freshly squeezed from a baker’s pastry bag.The flowers of the Mountain Laurel, an evergreen understory shrub, invite pollinators to stop by for a sweet treat.Little Wood-Satyrs (Megisto cymela) are patrolling forest edges looking for mates and, to host their eggs and larvae, the stands of grasses they find most suitable.Many of the species of small butterflies we call skippers are now active. The Zabulon Skipper can be found patrolling grassy forest edges, particularly near streams, ponds, and wetlands.Among the showiest of our butterflies, the Red-spotted Purple (Limenitis arthemis astyanax) is seen here on the leaves of a Black Cherry, its favored host plant.Another red-spotted Purple seen picking up minerals from a dried up puddle depression on a gravel road.Butterfly observers will do well to pay a visit to the new Susquehanna Riverlands State Park on Furnace Road north of Hellam in York County, Pennsylvania.Upon arrival at Susquehanna Riverlands, drive back the gravel road for about a mile to the parking area at the edge of the agricultural field. Then, hike the trail through the woods and farm hedgerow to the Schull’s Rock overlook on the river. In the forests along this route, the understory is dominated by colonial stands of Common Pawpaw trees.Along the lookout trail to Schull’s Rock, the Common Pawpaws’ large leaves help them to shade out potentially fast-growing competition. In proper growing situations, pawpaws develop clonal suckers that mature over time to create colonial stands of a single genetic plant.A Common Pawpaw understory along the approach to Schull’s Rock.A colonial stand of Common Pawpaw along the trail leading to Schull’s Rock.During our recent visit to Schull’s Rock, dozens of Zebra Swallowtails were seen along the trail, many in the vicinity of their sole host plant, the Common Pawpaw. But even more were observed along the edges of the fields and woods where nectar sources like this Multiflora Rose were being visited by numbers of butterflies we normally see only among abundant species like Cabbage Whites. Absolutely amazing!And the view of the Susquehanna and the Shock’s Mills railroad bridge at the mouth of Codorus Creek is pretty good too!You can look for colonial stands of Common Pawpaw at other parks and preserves along the lower Susquehanna as well. Birds like this Hooded Warbler can sometimes be found among them in mature riparian forests along the steep slopes of the river gorge.A Baltimore Oriole in a Common Pawpaw along a forest edge.Meanwhile in the treetops, the spring thrust of Neotropical migrants is drawing to a close. The Blackpoll Warbler is typically one of the last to transit the lower Susquehanna valley on its way to northern coniferous forests for summer. They’ve had an unusually protracted movement through the region this spring, the earliest individuals reported during late April. Though very difficult to see in the canopy of the mature trees where it feeds and sings, hearing one is often a benchmark for senior birders each spring. Older observers have often said of the Blackpoll Warbler’s high-pitched song, a rapid series of insect-like staccato “tseet” notes, that it was the first they could no longer detect as their ears started losing sensitivity.In many tracts along the lower Susquehanna this spring, the American Redstart is turning out to be the most common nesting warbler. Conditions favoring their reproductive success in recent cycles, as well as good survival rates during their migrations and stays on wintering grounds, have filled many lowland forests with redstart songs in 2025. Is this the start of a trend or just an exceptionally good year? Time will tell.Yet one more reason for a stroll in local forests this week is the chance to see and hear the Rose-breasted Grosbeak. Look for these Neotropical relatives of the cardinal nesting on territories in mature stands of deciduous trees like this Yellow Poplar, a species also known as the Tuliptree.They spend nearly all their time among the canopy foliage of the largest timber……but pause frequently to repeat a song often described as something akin to that which might be performed by a robin subjected to voice lessons. The Rose-breasted Grosbeak is certainly a bird worth seeing and hearing.
