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Red Knot

A species of Calidris, Also known as Robin Breast, Robin Snipe
Scientific name : Calidris canutus Genus : Calidris

Red Knot, A species of Calidris
Also known as:
Robin Breast, Robin Snipe
Botanical name: Calidris canutus
Genus: Calidris
Red Knot (Calidris canutus) Photo By Bettina Arrigoni , used under CC-BY-2.0 /Cropped and compressed from original

Description

An adult red knot is the second largest Calidris sandpiper, measuring 23–26 cm (9.1–10.2 in) long with a 47–53 cm (19–21 in) wingspan. The body shape is typical for the genus, with a small head and eyes, a short neck and a slightly tapering bill that is no longer than its head. It has short dark legs and a medium thin dark bill. The winter, or basic, plumage becomes uniformly pale grey, and is similar between the sexes. The alternate, or breeding, plumage is mottled grey on top with a cinnamon face, throat and breast and light-coloured rear belly. The alternate plumage of females is similar to that of the male except it is slightly lighter and the eye-line is less distinct. Canutus, islandica and piersmai are the "darker" subspecies. Subspecies rogersi has a lighter belly than either roselaari or piersmai, and rufa is the lightest in overall plumage. The transition from alternate to basic plumages begins at the breeding site but is most pronounced during the southwards migration. The molt to alternate plumage begins just prior to the northwards migration to the breeding grounds, but is mostly during the migration period. The large size, white wing bar and grey rump and tail make it easy to identify in flight. When feeding the short dark green legs give it a characteristic 'low-slung' appearance. When foraging singly, they rarely call, but when flying in a flock they make a low monosyllabic knutt and when migrating they utter a disyllabic knuup-knuup. They breed in the moist tundra during June to August. The display song of the male is a fluty poor-me. The display includes circling high with quivering wing beats and tumbling to the ground with the wings held upward. Both sexes incubate the eggs, but the female leaves parental care to the male once the eggs have hatched. Juvenile birds have distinctive submarginal lines and brown coverts during the first year. In the breeding season the males can be separated with difficulty (<80% accuracy in comparison to molecular methods) based on the more even shade of the red underparts that extend towards the rear of the belly. The weight varies with subspecies, but ranges between 100 and 200 g (3.5 and 7.1 oz). Red knots can double their weight prior to migration. Like many migratory birds they also reduce the size of their digestive organs prior to migration. The extent of the atrophy is not as pronounced as species like the bar-tailed godwit, probably because there are more opportunities to feed during migration for the red knot. Red knots are also able to change the size of their digestive organs seasonally. The size of the gizzard increases in thickness when feeding on harder foods on the wintering ground and decreases in size while feeding on softer foods in the breeding grounds. These changes can be very rapid, occurring in as little as six days.
Size
25-28 cm (10-11 in)
Colors
Brown
Black
Bronze
Gray
White
Orange
Life Expectancy
16 years
Nest Placement
Ground
Clutch Size
3 - 4 eggs
Incubation Period
1 brood
Number of Broods
21 - 23 days
Feeding Habits
Red Knot mainly consumes small bivalves, gastropods, and crustaceans, with season-specific prey such as horseshoe crab eggs in Delaware Bay and grunion eggs in western North America. During breeding, red Knot eats arthropods and spider larvae. Red Knot's tactile feeding technique involves probing mudflats, while visual hunting is used for mobile prey in the breeding season.
Habitat
Red Knot principally inhabit coastal areas, opting for tidal flats and shores. During breeding, they are found on dry High Arctic tundra with sparse vegetation, favoring sunny southern slopes. They adapt to wetter terrains near these breeding grounds for foraging. Post-breeding, red Knot shift to sedge meadows and lakeshores, intensifying feeding to fuel migration. Outside breeding, red Knot favor marine environments like sandy beaches, saltmarshes, estuaries, and mangroves, rich in invertebrates. Occasionally, red Knot can be found inland along lake shores or in freshwater marshes.
Nest Behavior
Red Knot exhibits nesting preparation by the male, selecting 3-5 sites. Once the female chooses a site, they line it with local plant material. Their behavior encompasses incubation and care for the young.
Nest Characteristics
Red Knot selects dry, stony tundra areas for nesting, often near ridges and wetlands with sparse vegetation. The female-lined nest scrapes average 4.7 inches across, 1.7 inches deep, and include grass, leaves, lichens, or heather.
Dite type
Aquatic invertebrate eater

Migration Overview

In the breeding season, the red knot has a circumpolar distribution in the high Arctic, then migrates to coasts around the world from 50° N to 58° S. The red knot has one of the longest migrations of any bird. Every year it travels more than 9,000 mi (14,000 km) from the Arctic to the southern tip of South America. The exact migration routes and wintering grounds of individual subspecies are still somewhat uncertain. The nominate race C. c. canutus breeds in the Taymyr Peninsula and possibly Yakutia and migrates to Western Europe and then down to western and southern Africa. C. c. rogersi breeds in the Chukchi Peninsula in eastern Siberia, and winters in eastern Australia and New Zealand. Small and declining numbers of rogersi (but possibly of the later described piersmai) winter in the mudflats in the Gulf of Mannar and on the eastern coast of India. The recently split race C. c. piersmai breeds in the New Siberian Islands and winters in north-western Australia. C. c. roselaari breeds in Wrangel Island in Siberia and north-western Alaska, and it apparently winters in Florida, Panama and Venezuela. C. c. rufa breeds in the Canadian low Arctic, and winters South America, and C. c. islandica breeds in the Canadian high Arctic as well as Greenland, and winters in Western Europe. Birds wintering in west Africa were found to restrict their daily foraging to a range of just 2–16 km (0.77–6.18 sq mi) of intertidal area and roosted a single site for several months. In temperate regions such as the Wadden Sea they have been found to change roost sites each week and their feeding range may be as much as 800 km (310 sq mi) during the course of a week. B95, also known as Moonbird, is a noted individual of the subspecies C. c. rufa. A male, he has become famous amongst conservationists for his extreme longevity — he was aged at least 20 as of his last sighting in May 2014.

General Info

Behavior

Red Knot exhibit a mixture of solitary and social behaviors based on their breeding and migratory cycles. During breeding, males perform impressive aerial displays and create multiple potential nest sites to attract mates, engaging in melodic song flights that reach great heights before gliding down while vocalizing. These displays are paired with ground behaviors like scrape showing and distinct postural changes for courtship. Once paired, red Knot are seasonally monogamous, and both sexes share the responsibility of incubation. Outside of breeding, they are gregarious, forming dense flocks during migration and wintering periods, often resting in close-knit groups on sandy grounds and conserving energy by lying on their bellies.

Distribution Area

In the breeding season, the red knot has a circumpolar distribution in the high Arctic, then migrates to coasts around the world from 50° N to 58° S. The red knot has one of the longest migrations of any bird. Every year it travels more than 9,000 mi (14,000 km) from the Arctic to the southern tip of South America. The exact migration routes and wintering grounds of individual subspecies are still somewhat uncertain. The nominate race C. c. canutus breeds in the Taymyr Peninsula and possibly Yakutia and migrates to Western Europe and then down to western and southern Africa. C. c. rogersi breeds in the Chukchi Peninsula in eastern Siberia, and winters in eastern Australia and New Zealand. Small and declining numbers of rogersi (but possibly of the later described piersmai) winter in the mudflats in the Gulf of Mannar and on the eastern coast of India. The recently split race C. c. piersmai breeds in the New Siberian Islands and winters in north-western Australia. C. c. roselaari breeds in Wrangel Island in Siberia and north-western Alaska, and it apparently winters in Florida, Panama and Venezuela. C. c. rufa breeds in the Canadian low Arctic, and winters South America, and C. c. islandica breeds in the Canadian high Arctic as well as Greenland, and winters in Western Europe. Birds wintering in west Africa were found to restrict their daily foraging to a range of just 2–16 km (0.77–6.18 sq mi) of intertidal area and roosted a single site for several months. In temperate regions such as the Wadden Sea they have been found to change roost sites each week and their feeding range may be as much as 800 km (310 sq mi) during the course of a week. B95, also known as Moonbird, is a noted individual of the subspecies C. c. rufa. A male, he has become famous amongst conservationists for his extreme longevity — he was aged at least 20 as of his last sighting in May 2014.

Species Status

Not globally threatened.
Red Knot (Calidris canutus) Red Knot (Calidris canutus) Photo By Bettina Arrigoni , used under CC-BY-2.0 /Cropped and compressed from original

Scientific Classification

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