biology

Red knot

Red knot is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Red knot rather than just read about it. In short: The red knot or just knot (Calidris canutus) is a medium-sized shorebird which breeds in tundra and the Arctic Cordillera in the far north of Canada, Europe, and Russia. It is a large member of the Calidris sandpipers, second only to the great knot.

Key takeaways

Red knot belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Red knot to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Red knot from memory before moving on to harder problems.

Reference excerpt

The red knot or just knot (Calidris canutus) is a medium-sized shorebird which breeds in tundra and the Arctic Cordillera in the far north of Canada, Europe, and Russia. It is a large member of the Calidris sandpipers, second only to the great knot. Six subspecies are recognised. Their diet varies according to season; arthropods and larvae are the preferred food items at the breeding grounds, while various hard-shelled molluscs are consumed at other feeding sites at other times. North American breeders migrate to coastal areas in Europe and South America, while the Eurasian populations winter in Africa, Papua New Guinea, Australia, and New Zealand. This species forms enormous flocks when not breeding.

Taxonomy, systematics, and evolution The red knot was first described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae as Tringa canutus. One theory is that it gets its name and species epithet from King Cnut; the name would refer to the knot's foraging along the tide line and the story of Cnut and the tide. There appears to be no historical foundation for this etymology. Another etymology is that the name is onomatopoeic, based on the bird's grunting call note.

The red knot and the great knot were originally the only two species placed in the genus Calidris, but many other species of sandpiper were subsequently added. A 2004 study found that the genus was polyphyletic and that the closest relative of the two knot species is the surfbird (Calidris virgata). There are six subspecies, in order of size:

C. c. roselaari (Tomkovich, 1990) (largest) C. c. rufa (Wilson, 1813) C. c. canutus (Linnaeus, 1758) C. c. islandica (Linnaeus, 1767) C. c. rogersi (Mathews, 1913) C. c. piersmai (Tomkovich, 2001) (smallest) Studies based on mitochondrial sequence divergence and models of paleoclimatic changes during the glacial cycles suggest that C. c. canutus is the most basal population, separating about 20,000 years ago (95% confidence interval: 60,000–4,000 years ago) with two distinct lineages of the American and Siberian breeders emerging about 12,000 years ago (with a 95% confidence interval: 45,000–3,500 years ago).

Distribution and migration

In the breeding season, the red knot has a circumpolar distribution in the high Arctic, then migrates to coasts around the world to winter at latitudes between 60° N (Shetland) to 55° S (Tierra del Fuego). The red knot has one of the longest migrations of any landbird. Every year some birds of C. c. rufa travel more than 14,000 km (9,000 mi) from the Arctic to the southern tip of South America and repeat the trip in reverse. 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 winter in 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 C. c. rogersi (but possibly of the later described C. c. 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 and Greenland, and migrates through Iceland to winter in Western Europe. Birds wintering in west Africa were found to restrict their daily foraging to a range of just 2–16 km2 (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 km2 (310 sq mi) during the course of a week. It is long-lived for a bird of its size; a bird ringed at Brora in northern Scotland as a first-winter in October 1978 (when 3–4 months old) was resighted still alive at Den Helder in the Netherlands in February 2006, 27 years, 3 months, and 29 days after being ringed. Another, tagged "B95" and nicknamed 'Moonbird', of the subspecies C. c. rufa, was at least 20 years old as of his last sighting in May 2014.

Description and anatomy

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Red knot

Start with the simplest possible case. Write down what Red knot claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Red knot before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Red knot ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Red knot

In research: Red knot appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Red knot in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Red knot is common in secondary-school and first-year university syllabi. It links to neighbouring topics Animal taxa named by Carl Linnaeus, Birds described in 1758, Birds of Africa, so understanding it makes those chapters shorter.
In everyday life: Look for Red knot outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Red knot in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Red knot means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Red knot out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Red knot in simple terms?

Why does Red knot matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Red knot?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Red knot.