Unexpectedly, the Delaware Bay beaches recorded the fewest red knots ever during this spring’s northward migration, raising questions about the shorebird’s long-term survival and undercutting 25 years of conservation work.
Less than 7,000 members of the bird’s rufa subspecies were tallied by conservationists in New Jersey and Delaware in extensive surveys conducted in May on land, air, and water.
Red Knots in Steepest Decline in Years, Threatening the Species’ Survival
The lowest percentage since the early 1980s, when there were about 90,000 people in the population, was about a third of the population in 2020, which is less than a quarter of the levels from the preceding two years.
The number of the bird was already much lower than what was required to ensure its survival. After years of conservation efforts, the state of New Jersey outlawed the taking of horseshoe crabs, whose eggs are necessary for the long-distance migration of the birds.
The most recent decline brings the rufa subspecies, which has been federally designated as threatened since 2014, closer to extinction in addition to making it more sensitive to external shocks like harsh weather in its Arctic nesting grounds, according to naturalists.
“We need to think of the red knot as a species that is dying and we really need emergency measures,” says Joanna Burger, a scientist at Rutgers University. She has researched the knot and other diminishing shorebirds on the Delaware Bay since the early 1980s, including ruddy turnstones and semipalmated sandpipers.
She urged the Atlantic States Marine Fisheries Commission to stop using horseshoe crabs as bait, a practise that is still carried out in Delaware, Maryland, and Virginia. Wildlife specialists claim that the fact that female crabs cannot be gathered has led to the extinction of some egg-laying crabs and a reduction in the availability of food for birds.
Naturalists have intensified their appeals for pharmaceutical companies to stop using LAL, an extract from crab blood that is used to detect pathogens in vaccinations, medications, and medical equipment, in the aftermath of the recent fall. Due to the unavailability of synthetic substitutes like rFC, which is utilised by at least one pharmaceutical business, horseshoe crabs have long been sought after.
According to conservationists, up to one-third of the crabs that are bleeding back into the water die or are unable to breed. This year there were lots of crab eggs on the bay beaches due to long-term losses in egg supply, but natural calamities have greatly reduced the bird population.
Larry Niles, a wildlife researcher who works alone, has been capturing, observing, and counting shorebirds on the bay beaches of New Jersey for the past 25 years. He was taken aback by the severity of the red knot count fall this year, which he relates to indications of a subpar mating season in 2020.
He thinks that the mid-cool Atlantic’s ocean temperatures will be to responsible for the migration in 2020. The chilly water caused horseshoe crab spawning to be postponed until early June, but by that time the birds had already left Delaware Bay in an effort to complete their migration.
Many of the avian species, which weigh only 4.7 ounces when fully grown, have already perished from malnutrition after taking flight from Tierra del Fuego in southern Argentina. Some people travel to the Delaware Bay by flying nonstop for seven days, followed by two weeks of recuperation and weight gain.
Unlike the previous year, when a large number of birds failed to locate food in the bay, this year’s migration of birds was in quest of breeding sites up north. Dr. Niles calculated that 40% of the migrants from the previous year died before they reached the Arctic because they ran out of food and water.
Due to the development of nesting platforms in New Jersey, peregrine falcons have also been held accountable for the species’ population drop this year. Shorebirds find it harder to eat and put on weight on the bay beaches as a result.
The best chance for the survival of the species, according to Dr. Niles, is a complete restriction on harvesting female horseshoe crabs until the population has recovered.
“Rufa knots, especially long-distance red knots, could be lost,” he claimed. Horseshoe crab populations can be grown despite the fact that harsh weather and cold water can’t be avoided, allowing birds to find an abundance of horseshoe crab eggs in most of these circumstances.