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RED KNOT (Calidris canutus)

an excerpt from Birder's Conservation Handbook

STATUS AND DISTRIBUTION

Species has a circumpolar breeding range occurring in Arctic Russia as well as in North America and Greenland. Three of the five described subspecies breed in North America. The roselaari subspecies has a disjunct breeding population in northwestern Alaska, including the Seward Peninsula. The rufa subspecies breeds in northern Nunavut and Northwest Territories, mostly on Arctic islands. The islandica subspecies breeds further east in Arctic Canada and along the coasts of Greenland. The exact distributional limits between the rufa and islandica subspecies are poorly delimited. An estimated 64% of the species total North American population is thought to breed in Canada, the remaining 36% in Alaska. Important breeding sites for the species in Canada include Southampton Island, King William Island (both for rufa subspecies), and northwestern Ellsmere Island (for islandica subspecies).

Perhaps the most important spring migratory stopover location in the U.S. is along the New Jersey and Delaware shores of Delaware Bay, where single-day counts as high as 96,000 have been recorded and an estimated 200,000 birds (50% of the North American population and virtually 100% of rufa subspecies) stop off to fatten up on horseshoe crab eggs. Other important spring staging areas include Alaska’s Copper River and Yukon-Kuskokwim Deltas (up to 100,000 may use either site in some years, representing 25% of North American population), Washington’s Gray’s Harbor and Willapa Bay (hundreds and occasionally thousands), California’s San Francisco Bay (up to 1,000), Texas’ Mustang Island Beach, Matagorda National Wildlife Refuge (NWR), and Bolivar Flats (hundreds and occasionally thousands), Saskatchewan’s Last Mountain Lake, Quill Lakes, and Chaplin Lakes (up to 2,500). Important stopover locations in South America include Argentina’s Bahia San Antonio Oeste (up to 20,000) and Brazil’s Lagoa do Peixe (up to 13,000). In fall migration, birds do not usually concentrate in high numbers at any one site and are more dispersed, though most of the spring staging areas are also used in fall.

Wintering range is extensive, extending from the Pacific and Atlantic coasts of U.S. south through Central America and the Caribbean to South America. Largest concentrations (rufa subspecies and possibly some of roselaari subspecies) are along the southern South American coast, with the largest numbers in coastal Chile and Argentina but significant numbers (estimated as high as 10,000) also in coastal Florida. A large proportion of the total wintering population of the rufa subspecies is thought to be concentrated within Chile’s Bahia Lomas. Other important sites include Argentina’s Bahia Lomas, Bahia San Sebastian, and Rio Grande.

Hundreds, sometimes thousands, winter along the coasts of California, Georgia, North Carolina, and South Carolina and in Baja California. Birds wintering in the U.S. and Mexico and at scattered locations throughout the Caribbean, Central America, and northern South America are thought to be from the roselaari subspecies. The bulk of the islandica subspecies winters along the coast of the North Sea in Europe and the United Kingdom, with nearly 90% of the wintering population in Britain and 50% in the Walsh Estuary alone.

Numbers of the rufa subspecies declined by more than 50% between the mid-1980s and 2003. The number of wintering islandica subspecies has stabilized in recent years but remains about 40% lower than in the 1970s. There is no information on trends in the roselaari subspecies. The species’ total North American population was estimated in 2000 at 400,000, with 170,000 in rufa subspecies, 150,000 in roselaari subspecies, and 80,000 in islandica subspecies. However, more recent estimates of the rufa subspecies put the total population as low as 35,000-40,000, which would put the total North American population at 265,000-270,000.

ECOLOGY

Breeds in Arctic lowlands near coasts on hummocks within wet habitats and in some locations and some years on higher ridges or gravel eskers. Nests are depressions on the ground where four eggs are laid and incubated by both the male and the female for 21-22 days. Young are precocial and leave the nest within hours after hatching and forage on their own. Usually only the male defends and broods the young. The young are estimated to fledge in 18 days. Only a single brood is produced each year. Feeds mostly on marine invertebrates, especially mussels in many areas. In Delaware Bay birds feed almost exclusively on the eggs of horseshoe crabs. When birds arrive in spring at Delaware Bay after their 9,000 mile journey from the southern South American wintering grounds they are very lean and must double their weight to be able to reach the Arctic breeding grounds and survive. Most birds are not thought to breed until at least two years old. On wintering grounds and during migration they prefer sandy beaches and intertidal flats.

THREATS

The major overriding threat has been human-caused decimation of horseshoe crab egg food supply at the key Delaware Bay staging area for the entire population of the rufa subspecies. The annual harvest of horseshoe crabs (to be used for bait) along the Atlantic Coast increased from about 800,000 pounds in 1993 to 6.38 million pounds in 1998 while towing surveys of horseshoe crab numbers in Delaware Bay went from an average of 6.8 crabs per tow in 1991 to 0.2 crabs per tow in 2002. In recent years an increasingly large proportion of the population passing through Delaware Bay has not been able to find enough horseshoe crab eggs to increase weight sufficiently for breeding and survival. This has resulted in a 37% decrease in adult survival rates and is thought to account for the dramatic declines in the population of the rufa subspecies.

Much of the species’ range in Alaska and Canada is within protected areas or areas with relatively undisturbed habitat. However, many breeding areas could be opened to oil and gas extraction activities. Such activities can cause habitat loss and degradation from establishment and expansion of infrastructure and pollution and increases in predatory mammals and birds (that capitalize on garbage). In 2004 a plan was released for consideration to open the 8.8-million-acre Northwest Planning Area of the National Petroleum Reserve-Alaska to leasing for oil and gas development. Oil and gas exploration and mining activity is expected to show increases within portions of the Canadian breeding range as well.

In migration and on wintering grounds the major threat is continued loss and degradation of coastal wetlands. In the U.S., such habitat loss has been dramatic. Florida and Texas have each lost at least 7.5 million acres of wetlands and Louisiana between 2.5 and 7.5 million acres over the last 200 years. In Louisiana and Texas coastal wetlands are continuing to be lost to erosion and subsequent saltwater intrusion. In California’s San Francisco Bay, 80% of intertidal habitats have been destroyed. South of the U.S., loss of coastal wetland habitat in many countries continues to be a major threat. At the major wintering area in Argentina, there is offshore oil exploration and extraction activity nearby, a spill from which would threaten the estuary.

Many estuarine systems used by Red Knot in migration and winter are showing degraded environmental conditions. For example, the percentage of the Delaware Estuary that tested above EPA ecological limits for metal contaminants increased from 5 to 22% form 1990-93 to 1997. The amount of land lost to development with the Delaware Bay Estuary increased 20% from 1970 to 1990. Clearly, any activities that result in loss or degradation of habitat, including alteration of water levels, destruction of buffer habitat, spraying of pesticides, ditching, accumulation of contaminants, grazing, or spread of invasive plants like phragmites, are continuing threats to the species. In many areas the species uses beach habitats that are increasingly threatened by development, beach armoring, and so-called beach renourishment projects. All of these activities reduce the invertebrate food supply that Red Knots and other beach-inhabiting birds rely upon. Sea level rise with global warming may become the most pervasive and difficult threat to the species. An estimated 16-33% of the species Arctic breeding habitat could be lost from global warming-induced sea level rise.

CONSERVATION ACTION

A coalition of conservation organizations has been actively working to decrease or stop the massive harvest of horseshoe crabs along the mid-Atlantic coast of the U.S. The National Marine Fisheries Service closed a 1,500-square-mile area at the mouth of Delaware Bay to harvesting of horseshoe crabs in 2001 and reduced harvest levels by 30%. Because horseshoe crabs do not begin breeding until 7-8 years of age it may require years before we know whether populations can reach former levels. The New Jersey Division of Fish and Wildlife established closures on important beach feeding areas for the species in May 2003 that restricted human presence on the beaches to prevent disturbance of feeding knots and other shorebirds.

Research efforts on the species on breeding, wintering, and migratory ranges have increased dramatically in the last decade. Thousands of birds have been banded in southern South America and during migration in Delaware Bay. Radio transmitters affixed to birds migrating through Delaware Bay allowed the discovery of the primary breeding areas and a research team has carried out annual studies of the species’ breeding biology since that time.

U.S. and Canadian shorebird conservation plans have been developed that provide recommendations for management, research, outreach, and education for Red Knot and other shorebird species. The Western Hemisphere Shorebird Reserve Network, RAMSAR Treaty on Wetlands, and the Birdlife International Important Bird Areas programs have identified many key breeding, wintering, and migratory stopover locations for the species and in some locations have initiated conservation and outreach projects.

A great many organizations, agencies, and coalitions are working on coastal habitat restoration and protection projects within the U.S., many of which will likely eventually benefit Red Knot. For example, the Coastal America Partnership, a coalition of federal agencies, state and local governments, and private organizations, identifies and implements local wetland restoration and protection projects throughout the U.S. The Partnership had initiated more than 500 projects impacting hundreds of thousands of acres of wetland habitat as of 2002. The Delaware Estuary Program is a broad partnership that is working to improve the health of the Delaware Bay ecosystem through a great variety of habitat restoration, conservation, outreach, and education projects. The Texas Prairies Wetlands Project was created by U.S. Fish and Wildlife Service, Texas Parks and Wildlife Department, USDA’s Natural Resource Conservation Service, and Ducks Unlimited to provide technical assistance and financial incentives to private landowners for improving or restoring wetland habitats along the Gulf Coast. Through January 1994, 4,901 acres of wetland projects had been completed or were under construction for 30 landowners, and 132 landowners controlling 1,231,023 acres had received on-site technical assistance. The Atlantic Coast Joint Venture (ACJV) has been very active in protecting winter habitat through a multitude of land acquisition and habitat restoration projects involving more than $230 million in grants and matching funds and nearly 300,000 acres of habitat. Audubon’s San Francisco Bay Campaign has proposed to restore over 100,000 acres of wetland habitat in the area over the next 20 years. A preliminary agreement with Cargill, Inc., would result in the public acquisition of 16,500 acres of salt ponds for $100 million. The ponds would eventually be restored to tidal wetlands.

CONSERVATION NEEDS

• Slow production of global warming pollution.
• Continue efforts to decrease commercial harvesting of horseshoe crabs along the mid-Atlantic coast of U.S.
• Continue efforts to reduce disturbance of birds at important migratory feeding areas.
• Ensure that management of publicly owned locations currently supporting the Red Knot continues to maintain habitat conditions beneficial to the species.
• Increase protection, conservation, and restoration of coastal habitat within the migration and wintering range of the Red Knot.
• Implement further wintering surveys of the species in U.S., Mexico, the Caribbean, and Central and South America.

To learn more about the red knots critical state, click here to read how several groups are fighting to protect the red knot.

Click here to buy Jeff Wells' book, The Birder's Conservation Handbook.