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Dieren en planten

Waders   Sandpipers   Little stint   Dunlin   Sanderling   Red knot   Birds   Top bird region   

Red knot

size:

length: 23-25 centimeters
wingspan: 47-54 centimeters

weight:

140 grams

color:

summer: red-brown
winter: gray-white

age:

record: 28 years

food:

winter: small shellfish, crustaceans, worms and snails
summer: insects, spiders and seeds

reproduction:

maturity: 1 year
number of eggs: 4

  • Dut: Kanoetstrandloper (kanoet, knoet)
  • Eng: (Red) Knot
  • Fren: Bécasseau maubèche
  • Ger: Knutt
  • Dan: Islandsk ryle
  • Nor: Polarsnipe
  • Fries: Mients
  • Ital: Piovanello maggiore
  • Lat: Calidris canutus
  • Dan: Islandsk ryle (Calidris canutus canutus, Calidris canutus islandica)
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Red knot (winter), Jeroen Reneerkens (jeroenreneerkens@hetnet.nl)

Red knot

Red knots are plump sandpipers with a short neck and sturdy legs. They are totally specialized in finding shellfish, Baltic tellins being their favorite. When they look for food, you see them slowly moving over the flats with their head bent down and the tip of their bill pushed into the mud. All of the red knots combined eat around 1.5 million kilograms of shellfish meat per year from the Dutch tidal flat bottom.

  • King Canute
    Knots in flight, Jeroen Reneerkens

    The red knot is named after the Danish king Canute, ruler of the countries around the North Sea in olden times, who attempted to stem the waves. One thing the king and the bird had in common: they both had to deal with the tides along the coast.

  • An unusual bill
    Knot (summer plumage), Jeroen Reneerkens (jeroenreneerkens@hetnet.nl

    The knot finds its food in an unusual manner. The bird is able to feel a shellfish with its beak as deep as 10 centimeters by measuring pressure differences around the object in the wet sand. Up till now, the red knot is the only species known to gather its food in this manner. Other sandpipers catch worms by feeling vibrations with their beak in the sand. Because the pressure differences can only be felt in wet sand, it is obvious why knots never look for food on dry tidal banks. In their nesting areas, knots eat insects.

  • Odor camouflage
    Knutt, Island, Jeroen Reneerkens

    Knots protect their plumage with a waxy substance which is made in a gland by their tail bone. During brooding season, the consistency of this wax changes so that it doesn't give off as much odor. This makes it more difficult for the Arctic fox and other predators to find them as easily.

  • Strongly fluctuating numbers
    Number of knots counted in the winter, Ecomare

    From the graph, you can see how varying the numbers of knots can be in the Dutch Wadden Sea during the winter. The fluctuations are due to the fluctuating amount of shellfish available.

  • Yoyo effect

    Knots need lots of energy reserves in the form of fatty tissue to make such long voyages. It takes around a month for a knot underway to Africa to build up a fat supply in the Wadden Sea. Just before departing, the bird weighs around 150 grams; that is twice as much as upon arrival, after a flight of a few thousand kilometers several days later. The knot digests unnecessary organs during the trip, such as the stomach. The heart and lungs, on the contrary, increase in size.

  • Distribution and habitat

    Red knots are bonded to seacoasts. The salt water protects them from various illnesses, which they will incur if they visit fresh water. The knots use the Netherlands as a place to rest during migration, or as a winter home. Large groups are seen in the Wadden Sea particularly during bird migration. It is an important tanking station for them. They fill up with shellfish and crustaceans to provide themselves with sufficient energy to continue their travels. Knots nest far north in Greenland and Siberia.

  • Find the differences

    Two subspecies of knots can be found in the Wadden Sea: those that nest in Canada or Greenland and migrate via Iceland to the Wadden Sea where they remain for the winter; and those that migrate from Siberia via the Wadden Sea to West-Africa, where they spend their winter.

  • Tank station

    Knots use the Wadden Sea as a tank station during migration in the spring and fall. The Wadden Sea is an important stop between their nesting grounds in the high north and the winter home. They rest and fatten up for the second part of the voyage. The declining food supply in the Wadden Sea therefore threatens to become an obstacle for the knots. Between 1996 and 2005, wintering knots lost more than half of their suitable feeding grounds. During that period, the number of knots in the Wadden Sea also declined by almost 50%. Some of the knots died, others found alternative wintering grounds in England and France. In order to better understand how the knots forage for food in the Wadden Sea, scientists provided around 50 birds with a transmitter in 2011. This makes it possible for them to follow the birds up to an accuracy of 10 meters using special reception stations in the Wadden Sea.