Red Knot

(Calidris canutus) (REKN)

Photographic Identification Guide

Red Knot (Calidris canutus) (REKN) is a circumpolar species with six described subspecies. These populations nest in patchy breeding sites around the northernmost coasts of the northern continents, and winter on nearly all oceanic coasts in both northern and southern hemispheres. Migration distances for some populations of this species exceed 9000 miles (15,000 km) per season.

Spectacular in its cinnamon-colored breeding garb and absolutely unremarkable in its gray winter plumage, REKN was a relatively common migrant on New England shores historically. It has undergone drastic drop-offs in migratory populations in the past 4 to 5 decades. Migrating REKN in spring, along with Ruddy Turnstone (RUTU), Sanderling (SAND) and other shorebird species, depend heavily on a feast of Horseshoe Crab eggs in Delaware Bay. This food resource has been reduced due to human hunting and killing of Horseshoe Crabs for use in medical labs and for fishing bait and pet food. Many of the birds, deprived of a rich food resource, are either unable to complete their migration to the Arctic where they breed, or once there, do not have enough fat reserves to breed successfully.

The State of New Jersey has limited human access to some of the beaches where Horseshoe Crabs come ashore in May to spawn. This has resulted in limited but noticeable reduction in the rate of population decline in affected shorebird populations.

In this guide, we cover the features, in order of importance, to look for on these birds. When discussing plumages, we use the terms winter, spring, and summer to refer to northern hemisphere seasons. Because some of these birds spend parts of the year in the northern and southern hemispheres, the correct technical terms for the plumage stages—basic and alternate—help avoid the confusion of seasonal terminology.

visual gallery

species account

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Fig. 1. Red Knot. Winter (basic) plumage. Bolivar Peninsula, TX. 13 April 2017.
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Fig. 4. Red Knot. Spring (alternate) plumage. Note complex back (mantle) feather patterns. Bolivar Peninsula, TX. 11 May 2015.
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Fig. 5. Red Knots. Flock of juveniles, one adult with worn summer (alternate) plumage. Plymouth Beach, Plymouth, MA. 28 August 2014.
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Fig. 7. Red Knots. Left: juvenile in fresh plumage. Right: Worn summer (alternate) plumage. Plymouth Beach, Plymouth, MA. 28 August 2014.
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Fig. 9. Red Knot. Juvenile. Note uniquely patterned back (mantle) feathers (inset). Nahant Beach, Nahant, MA. 22 August 2014.
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Fig. 6. Red Knot. Summer (alternate) plumage with worn back (mantle) and faded cinnamon belly feathers. Plymouth Beach, Plymouth, MA. 28 August 2014.
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Fig. 13. Comparison of Black-bellied Plovers, Short-billed Dowitchers and Red Knot. Molting adult Red Knot stands out due to gray back and pale belly suffused with cinnamon color. South Beach, Chatham, MA. 14 August 2023.
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Fig. 2. Red Knots in early spring. Left bird in winter (basic) plumage. Right bird mid-molt to spring (alternate) plumage. Bolivar Peninsula, TX. 13 April 2017.
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Fig. 8. Red Knot. Summer (alternate) molting to winter (basic) plumage. Plymouth Beach, Plymouth, MA. 28 August 2014.
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Fig. 3. Red Knots in early spring. Upper bird in winter (basic) plumage. Lower bird mid-molt to spring (alternate) plumage. Bolivar Peninsula, TX. 6 May 2019.
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Fig. 11. Comparison of Dunlin, Red Knot and Sanderlings. Note distinctive subterminal dark lines on Red Knot back (mantle) feathers. Winthrop Beach, Winthrop, MA. 1 October 2016.
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Fig. 12. Comparison of Red Knots and Sanderlings in flight. Note mostly pale, lightly barred tail, pale stripe on gray wings of Red Knots. Parker River NWR, Newburyport, MA. 6 September 2020.
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Fig. 10. Comparison of Red Knot juvenile and Sanderlings. Note size and leg-color differences. Plymouth Beach, Plymouth. 13 August 2019.

The photos in this species account are arranged in this order:

Basic: winter plumage, roughly October to March.

REKN begin the molt to winter (basic) plumage in September and usually complete it by the end of the calendar year; see Fig. 1.

Alternate: first spring and summer after hatch year or adult breeding plumage, March to August.

Beginning in spring, winter (basic) feathers on REKN are gradually replaced by spring (alternate) feathers; see Fig. 2, Fig. 3, Fig. 4. Replacement of alternate feathers by winter (basic) plumage begins in the fall; see Fig. 8.

Juvenile: young birds, recently hatched, June to September.

The distinctive juvenile mantle feathers are acquired on the breeding grounds immediately after the natal down is shed and before the young begin their southbound migration; see Fig. 9. In the fall, juvenile feathers begin to be replaced by winter (basic) plumage.

Size and weight

There are multiple subspecies of REKN breeding in circumpolar regions, with two recognized in North America. The dimensions below are for C. c. rufa, which is the primary migrant through eastern North America. Females are larger and have longer bills.

Body length:

9–10 in. (23–25 cm)

Wingspan:

22.75–24.5 in. (57–61 cm)

Bill length:

1.3–1.5 in (33–39 mm)

Weight:

4.4–7.2 oz. (125–205 g)

Calls

Red Knots have the reputation for elaborate territorial songs when displaying over their nesting sites. While in migration through our region, however, the birds are mostly silent, though at times they make short, soft squawking sounds.

Calls in Sinaloa, MX, 2019:

Calls in Brevard County, FL, 2013:

Plumage and other characteristics

Winter (basic) mantle feathers are gray with sharp, dark centers and very narrow pale margins. Overall, upperparts plumage is uniformly gray with a faint gray hood over the head, neck and down the upper breast. Breast and belly are lightly streaked. Lower flanks show dark gray squiggles; see Fig. 1.

In the spring, alternate cinnamon and black feathers begin to replace the winter (basic) mantle feathers. Belly, breast, neck and head develop a cinnamon suffusion; see Fig. 2, Fig. 3.

Full spring (alternate) mantle in May and later consists of intricately patterned, bright cinnamon, black and gray feathers with pale margins. Belly, breast and head are cinnamon-rufous; see Fig. 4.

Spring (alternate) plumage on birds reaching their first year of life (fledged the previous summer) is less colorful than alternate plumage on breeding-aged birds two years old or older. Some nonbreeding first-year birds may keep winter (basic) plumage into the spring and summer; see Fig. 2 and Fig. 3.

Spring (alternate) and summer (alternate) are the same plumage; however, as seasons advance, feather margins become worn, colors fade and the plumage looks different.

In the summer, alternate feathers lose much of their pale and cinnamon edging. On adult birds returning from the Arctic in July and August, worn mantle feathers have dark, almost black centers with narrow pale margins; see Fig. 5, Fig. 6, Fig. 7.

In August, summer (alternate) feathers begin to be replaced by gray winter (basic) feathers. Cinnamon coloration on the head and underparts fades and new pale feathers come in; see Fig. 8.

Newly fledged young birds acquire distinctive juvenile plumage. Each gray mantle feather has a narrow pale margin and a very narrow dark subterminal line paralleling the margin. The neck and upper breast are faintly streaked. When fresh, there is a pale suffusion of buff on the breast and belly; see Fig. 9.

Birds that winter in the northern hemisphere complete their molt in December and birds that winter in the southern hemisphere continue molting in the northern winter months (southern summer).

In flight, REKN displays a pale wing stripe from above. The tail is light gray and barred. The underwing is gray; see Fig. 12.

Winter REKN in flight displays off-white throat, neck and upper breast.

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Breeding range, migration, wintering range, habitat

During migration, foraging Red Knots feed on sandy or muddy beaches and shallow coastlines. Aside from Horseshoe Crab eggs, the birds feed on snails, other mollusks, crustaceans and worms.

On the nesting grounds, Red Knots forage on insects, snails and worms.

During migration, at higher tides they roost in dense flocks on higher dunes, sometimes on rock jetties or breakwaters.

REKN breeding areas have a patchy circumpolar distribution. In North America, REKN nests in far northwestern Alaska, on the northeastern Canadian Arctic islands north of Hudson Bay and on the coasts of Greenland.

After nesting, females appear along the coasts of the Canadian Maritimes, New England and the mid-Atlantic by late July, flying directly from the Arctic. Males stay behind to tend to the young for a short while, then follow females. Young birds begin appearing on the coasts of Maritime Canada and northeastern U. S. by mid-August.

During migration, REKN is a highly coastal species. There are very few inland records for the species.

Once the birds have foraged on coastal mudflats and beaches and built up sufficient fat reserves, most depart from the Canadian Maritimes and the northeast U. S. coast directly over the Atlantic Ocean toward South America. Wintering areas comprise most of the coast of South America, particularly the area at the southern tips of Argentina and Chile (Tierra del Fuego). A major wintering area is in Bahia Lomas in Chile, near the Straits of Magellan.

Smaller numbers of REKN winter along the coasts of Central and North America, particular in coastal Florida and the Gulf of Mexico.

In spring, migrant flocks of REKN streaming north gather at the shallow edges of Delaware Bay where Horseshoe Crabs spawn. Along with migrant Sanderlings, Ruddy Turnstones and other shorebirds, Red Knots fatten up on crab eggs before heading to the Arctic to nest.

Similar species

REKN compared to SAND

Red Knot (REKN) and Sanderling (SAND) often seek similar habitats to feed in or roost.

Note the following:

REKN is nearly twice the size of SAND; see Fig. 10.
In spring and summer (alternate) plumage, Red Knot has an evenly colored cinnamon belly, chest, neck and head; see Fig. 4. SAND alternate plumage is a speckling of rufous and black; see SAND Fig. 6.
REKN juvenile often has a buffy wash overall, with some streaking and speckling. Juvenile SAND underside is pure white from throat to tail; see Fig. 10, Fig. 11.
REKN juvenile is gray with narrow dark subterminal lines on each mantle (back) feather; see Fig. 9. SAND juvenile mantle plumage is a bold checkered black-and-white; See SAND Fig. 9.
In flight, winter (basic) REKN is much larger and very gray above, with gray underwings and a narrow pale wing stripe. SAND is much paler on the mantle (back), completely white underneath, and has a strong white wing stripe and white outer tail feathers; see Fig. 12.

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REKN compared to DUNL

Red Knot (REKN) is much larger than Dunlin (DUNL). DUNL, however, has a much longer bill.

Note the following:

In spring and summer (alternate) plumage, REKN has a smooth cinnamon head, neck, breast and belly; see Fig. 4. DUNL has a rusty crown and rufous-and-black mantle with a black belly; See DUNL Fig. 8.
In the fall, although both REKN and DUNL are grayish, the distinctive patterned look of REKN back (mantle) feathers with their subterminal dark lines stands out; see Fig. 11.
Though much reduced in numbers in recent years, fall migrant Red Knots arrive in coastal New England (primarily Monomoy Island off Cape Cod) in mid-July and remain into the early fall. Dunlin do not appear in New England in any numbers until October.
In all plumages, REKN bill is sturdy and straight, barely as long as the head; See Fig. 1. DUNL bill is curved, tapered and distinctly longer than the head; See DUNL Fig. 1.

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REKN compared to dowitcher

Red Knot (REKN) and dowitchers—Long-billed (LBDO) and Short-billed (SBDO)—are similar in body shape and size. Spring and summer (alternate) plumage for all these birds is colorful and winter (basic) plumage is gray or brownish gray. Fig. 13 presents a comparison of several shorebird species including REKN and SBDO.

Note the following:

Dowitcher bill is easily twice as long as REKN bill; see Fig. 1 and SBDO Fig. 1.
Alternate-plumaged REKN is unpatterned cinnamon on head, neck and belly; see Fig. 4. Dowitcher head, neck and breast in alternate plumage are peach and rusty-speckled; see SBDO Fig. 4.
Juvenile REKN plumage is distinctive; pale gray mantle feathers with narrow dark lines paralleling the edges; see Fig. 9. Short-billed Dowitcher juvenile is colorful and specked rusty and gray with conspicuous brown squiggles on the tertial feathers (the longest feather lying on top of the tail when resting); see SBDO Fig. 13. Long-billed Dowitcher juvenile is grayish with plain brown tertial feathers.
In flight, REKN has a gray-barred tail; see Fig. 12. Dowitchers have gray-barred tails and a narrow white stripe up the center of the back; see SBDO Fig. 16 and SBDO Fig. 17.
In flight, REKN has a pale gray wing stripe nearly the whole length of the wing; see Fig. 12. Dowitcher secondary feathers are white-tipped so that in flight, dowitchers display a pale trailing edge to the inner half of the wings; see SBDO Fig. 16 and SBDO Fig. 17.

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