Horseshoe crabs and their shorebird partners
May 21, 2026
The warm sand along Jamaica Bay holds the weight of an ancient ritual. Atlantic horseshoe crabs emerge from deeper waters as the spring tides peak, their dome-shaped shells catching the late afternoon light. These are not crabs at all, but arthropods older than the trees, older than the flowers, carrying in their bodies a design that has worked for hundreds of millions of years. The females, heavy with eggs, lumber toward the high tide line while smaller males cluster around them, their movements deliberate and unhurried.Each female horseshoe crab digs shallow nests in the wet sand, depositing thousands of pale green eggs the size of caviar. The eggs lie in clusters just beneath the surface, warmed by sand that holds the day's heat. What seems like a simple reproductive act becomes the foundation for one of the coast's most critical feeding relationships. The timing is everything. These eggs appear precisely when exhausted shorebirds arrive from their long journey north, their fat reserves depleted, their bodies demanding the specific proteins that will fuel the final push to Arctic breeding grounds.Northern parulas, small warblers with blue-gray backs and yellow throats, drop from the canopy to feed along the wrack line where storm waves have scattered horseshoe crab eggs like scattered pearls. Laughing gulls wheel overhead, their harsh calls echoing across the water as they dive for the protein-rich clusters. The eggs contain exactly what these migrants need: concentrated energy in a form their bodies can process quickly. A single female horseshoe crab may lay twenty thousand eggs. Most will feed the birds that depend on this seasonal abundance. The relationship works because it has worked for so long. The horseshoe crabs spawn in numbers that can sustain both their own reproduction and the appetites of arriving migrants. The shorebirds time their journey to coincide with this brief window of plenty.The evening light shifts from gold to amber across Jamaica Bay. Horseshoe crabs continue their ancient procession along the tide line, their tracks crisscrossing in the wet sand. Above them, northern parulas call from the newly leafed oaks, their thin notes carrying across water that reflects the deepening sky. The laughing gulls have settled for the night, but their presence lingers in the scattered shells and the small depressions where they landed to feed. Tomorrow the cycle continues, eggs and appetite meeting at the edge of land and water, where the rhythm of tides measures time in the oldest currency the coast knows.
Diamondback terrapins cross into nesting season
June 27, 2026
Along the brackish edges of the Hackensack Meadowlands, the tidal marsh grasses stand full and green in the longest days of the year. The water is warm. The mud at the marsh edge holds heat through the night. And on the sandy berms and upland margins that border these wetlands, female diamondback terrapins are emerging from the water to nest.The diamondback terrapin is the only turtle in North America that lives exclusively in brackish water, the mix of salt and fresh that defines estuaries like this one. She spends most of her life in the tidal creeks and coves of the Meadowlands, eating periwinkles, fiddler crabs, and mussels, moving with the tides. But in early summer, something shifts. Females become restless and begin to move toward shore. They are looking for dry, sandy, well-drained ground, often above the high tide line, where soil temperatures are warm enough to incubate eggs. A female may travel several hundred meters from the water's edge. She crosses roads. She pushes through beach grass. She excavates a flask-shaped cavity with her back feet, deposits four to eighteen eggs, fills the nest in, and returns to the water. The whole process can take less than an hour.What makes this moment ecologically significant is how exposed it is. In the water, a terrapin is difficult to catch. On land, she is slow, conspicuous, and committed. Common grackles and black-crowned night herons, both present along these wetland margins right now, are capable of taking hatchlings. Raccoons and foxes find and excavate nests with regularity, sometimes destroying a high percentage of eggs in a given area. Roads are the other pressure. The sandy, elevated ground terrapins prefer for nesting often sits on the far side of a road from the water, and females are struck by vehicles during the crossing. In places where terrapin populations have been studied along the northeastern coast, road mortality of nesting females has been one of the primary drivers of population decline, because females reproduce slowly. A female terrapin does not reach sexual maturity until she is seven to ten years old. She may live for more than twenty-five years. Each adult female lost to a car represents decades of potential reproduction removed from the population.The eggs themselves incubate for roughly sixty to seventy-five days, depending on soil temperature. Warmer nests develop faster. The sex of the hatchlings is also determined by temperature during a critical window mid-incubation: warmer conditions produce more females, cooler conditions more males. Nests that receive full sun through late summer will skew female-heavy. This temperature-dependent sex determination means that the aspect and shade cover of a nesting site shapes the population's future composition. When hatchlings emerge in late summer, they are small enough to fit in a tablespoon. Many move toward the water immediately. Some overwinter in the nest and emerge the following spring.The Hackensack Meadowlands hold one of the more significant terrapin populations remaining in the region. The estuary provides the right combination of brackish tidal habitat and upland nesting areas, though development has reduced and fragmented both. Terrapins here share their wetland margins with red-winged blackbirds singing from the phragmites tops, with great blue herons standing still in the shallows, and with ospreys working the open water above. All of these species are part of the same tidal system, drawing on the same productive estuary in different ways. The terrapin's role is particular: she moves nutrients and energy between the water column and the upland, and her eggs, whether they hatch or are predated, become part of the terrestrial food web above the tide line.If you are near any of the tidal margins around Jersey City right now, look at the sandy edges, the gravel shoulders near marsh, the dry elevated ground above the water. A nesting female leaves a distinctive track, a wide drag mark with alternating flipper prints on either side. The morning light is still low enough to cast shadows across the ground. You might find one.
