Each year, the Palmetto State plays a vital role in one of Mother Nature’s most impressive feats, when countless red knots flock to the S.C. coast as part of their annual 19,000-mile migration. After leaving their South American wintering grounds, these brilliantly colored shorebirds arrive on our shores in early March to feast on clams, mussels and horseshoe-crab eggs before heading to their Arctic nesting grounds in May and early June.
Thanks to a growing body of research, our knowledge about these medium-size shorebirds is expanding all the time. For instance, we know that as many as 41% of the remaining red knot population touches down on Seabrook and Kiawah islands each spring, according to a study published by Pelton, et al., this year in bioRxiv. Research conducted in 2018 by coastal bird biologists at the South Carolina Department of Natural Resources also found that two-thirds of the red knots that visit our state each year use South Carolina as their final U.S. stopover on their long northward journey.
Statistics like these demonstrate just how significant our state is in the lifecycle of these remarkable animals. Unfortunately, red knot populations have declined a staggering 87% since 2000, and more than 94% since the 1980s in some areas of the Atlantic Coast. In 2014, the U.S. Fish and Wildlife Service listed the species as federally endangered, pointing to three primary factors contributing to its decline: human and predator disturbance, habitat loss from sea level rise and development, and reduced prey availability. We at Audubon South Carolina, along with other like-minded organizations and individuals, are committed to addressing these threats to give red knots a fighting chance at survival.
To limit human and predator disturbance to shorebirds, we work hard to educate beachgoers about the importance of red knots and other vulnerable bird species. With the help of hundreds of trained volunteers known as Audubon Shorebird Stewards, we post informational signs, mark off sensitive habitat and educate the public on how to share the shore safely with birds. Without this information, people and pets can unwittingly frighten or “flush” coastal birds by chasing them or simply walking too close. As a result, red knots waste precious time and energy fleeing perceived threats rather than eating the food they need to survive their long migration.
To address habitat loss from rising seas and development, it’s important to protect the last remaining slivers of undeveloped coast that red knots need to survive. In Charleston County, this includes places such as Cape Romain National Wildlife Refuge and Crab Bank and Deveaux Bank seabird sanctuaries, and even residential communities such as Seabrook Island’s north beach.
Finally, growing scientific evidence points to lack of prey species availability as perhaps the greatest threat to red knot survival. Although red knots eat many different types of marine invertebrates, research shows they prefer horseshoe-crab eggs, probably because they are two to three times more nutrient-dense than other food sources.
It might surprise some to learn that the greatest competition for this critical red knot food source is the U.S. biomedical industry, which relies on a unique component in horseshoe crab blood to test the purity of medicines and equipment. Since the start of the pandemic, horseshoe crab harvesting has increased sharply to keep pace with soaring demand, creating serious concerns for both horseshoe crab and red knot populations. In addition to diminishing a most critical food source, the process of harvesting crabs itself can disturb red knot foraging.
To fully understand and address the problem, Audubon South Carolina supports greater transparency among all public and private parties involved in horseshoe crab harvesting. For instance, having access to data that show how many horseshoe crabs are collected and from where, as well as horseshoe crab mortality rates and egg density levels in the sand, can identify a definitive path toward helping the red knot population recover. We also support the federal Fish and Wildlife Service’s full list of proposed critical habitat areas for red knot, which would create greater protections for the species.
The challenges that red knots and other coastal birds face are immense but not insurmountable. The fate of this amazing species, and so many others, is in all our hands. Please do your part by sharing the beach with shorebirds, advocating for habitat protection and encouraging your elected officials to support greater transparency in horseshoe crab harvesting data.
Nolan Schillerstrom is Audubon South Carolina’s coastal program manager.