At Reeds Beach, New Jersey, on the night of May 23, the high tide receded across an apron of coarse sand densely studded with the blue-green eggs of spawning horseshoe crabs. By dawn, the beach held an estimated 19,000 rufa red knots in a tight, churning feeding flock that ran from the water's edge to the dune line and back.
Dr. Lawrence Niles, who has counted shorebirds on the Delaware Bay since 1986, called the figure the best single-site count he has logged since 2015.
Across the bay, on the Mispillion Harbor mudflats in Delaware, his colleague Wendy Lawson recorded 14,700 knots in the same dawn window. The full bay-wide peak count, completed by a sixteen-person team over the last week of May, came in at 38,400 birds.
The Rufa red knot, Calidris canutus rufa, breeds in the Canadian central Arctic and winters as far south as Tierra del Fuego. The Delaware Bay is the single most important stopover on the spring migration. The birds arrive lean, refuel for ten to fourteen days on the eggs of spawning horseshoe crabs, and depart for the Arctic with a doubled body mass.
The species was federally listed as threatened in 2014 after a roughly 75 percent population collapse over the preceding two decades. The collapse coincided exactly with the rise of the horseshoe crab harvest for commercial bait, which removed adult breeding crabs faster than they could be replaced.
By 2003, peak bay counts of red knots had fallen below 15,000. The shorter, denser feeding window was producing birds that arrived at the Arctic breeding grounds with insufficient fat reserves and, in some years, failed to breed at all.
Recovery has been slow and uneven. The horseshoe crab harvest was reduced through a series of state-level measures starting in the mid-2000s. The Atlantic States Marine Fisheries Commission's Adaptive Resource Management framework has progressively tightened the female bait quota since 2013.
The bait quota for 2026 was set at zero female crabs from Delaware Bay-origin stocks, a reduction from quotas that were still permitting tens of thousands of females as recently as 2019.
The bay's biomedical industry, which bleeds live horseshoe crabs to extract the clotting agent limulus amebocyte lysate for pharmaceutical testing, remains a contested factor. Bleeding mortality is estimated at between 10 and 30 percent of bled animals. The industry's annual take has been roughly half a million crabs in recent years.
A synthetic alternative to LAL, recombinant Factor C, was approved by the United States Pharmacopeia for general use in 2024 after two decades of regulatory work. Adoption by pharmaceutical manufacturers has been faster than industry skeptics predicted but slower than conservation advocates hoped.
What the May 2026 count reflects, Niles believes, is the cumulative effect of multiple converging interventions over the better part of a decade rather than any single management win. The crabs are recovering. The bait take is down. The recombinant uptake is reducing biomedical pressure. The bay's ecology is reorganising itself toward a slightly older state.
The knots benefit immediately. The eggs they consume are produced by females whose abundance the long management effort has begun to restore.
The team's standard refuelling-rate measurement, conducted by trapping a sample of birds at the midpoint of the stopover and re-trapping them three to five days later, recorded mean daily mass gains of 6.1 grams per bird through the third week of May. The threshold considered adequate for successful Arctic departure is roughly 4 grams per day.
Niles described the 6.1 figure as not seen in years.
The complications are real and worth noting. The rufa subspecies winters in widely separated regions, and the Tierra del Fuego wintering population has shown less recovery than the populations wintering in the southeastern United States. The Arctic breeding grounds have warmed measurably, and snowmelt timing affects both nest success and prey availability for the breeding adults.
A good Delaware Bay year does not guarantee a good Arctic breeding season. It only makes one possible.
The bay-wide count team will reconvene in September for the southbound migration, when juvenile birds returning from their first Arctic summer pass through the bay in much smaller numbers and in a more dispersed pattern.
The September count is the population's clearest signal of breeding success. The team has, after this spring's count, allowed itself a measure of guarded optimism that the September figures will be among the better of the last fifteen years.
Niles, finishing the morning's tally on the bed of his pickup at Reeds Beach, did not say recovery. He said improvement. He said the data will say whether it is improvement that holds.
