Source: Red Knots in Steepest Decline in Years, Threatening the Species’ Survival – The New York Times
Larry Niles, an independent wildlife biologist who has trapped, monitored and counted shorebirds on the bay beaches of New Jersey for the last 25 years, said he had been expecting some decline in this year’s red knot count because of signs of a poor breeding season in 2020, but was shocked by the size of the drop.
He said it’s likely traceable to low ocean temperatures in the mid-Atlantic during the 2020 migration. The cold water delayed the spawning of horseshoe crabs until early June, by which time the birds had already left the Delaware Bay in an attempt to complete their migration.
Many of the birds, weighing only 4.7 ounces when mature, are already emaciated after flying from Tierra del Fuego in southern Argentina in one of the longest migrations in the avian world. Some fly nonstop for seven days before reaching the Delaware Bay where they typically stay for about two weeks to rest and regain weight.
But last year, many were unable to find food on the bay, and so continued northward in an attempt to reach their breeding grounds. Dr. Niles estimated that around 40 percent of last year’s migrants died before they reached the Arctic, simply because they ran out of energy.
This year, he also blamed predation by peregrine falcons, whose growing coastal population has been helped by the construction of nesting platforms by New Jersey. They frequently hunt over the bay beaches, making it harder for flocks of shorebirds to feed and put on weight.
The best hope for the species to survive lies in a complete ban on harvesting female horseshoe crabs until the crab population recovers, Dr. Niles said.
“Rufa knots, especially long-distance red knots, could be lost,” he said in a note to supporters. “We can’t stop bad winds or cold water, but we can expand the population of horseshoe crabs, so birds arriving in most of these conditions find an abundance of horseshoe crab eggs.”
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