Knutt

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Knutt
Knutt (Calidris canutus) in breeding dress

Knutt ( Calidris canutus ) in breeding dress

Systematics
Order : Plover-like (Charadriiformes)
Family : Snipe birds (Scolopacidae)
Genre : Sandpiper ( Calidris )
Type : Knutt
Scientific name
Calidris canutus
( Linnaeus , 1758)

The red knot ( Calidris canutus ), also known as red knot sandpiper , is a bird from the family of snipe birds (Scolopacidae). It may have been named after the Anglo-Scandinavian King Canute the Great , but an onomatopoeic name after the sound of his calls is also conceivable.

The knot is a year-round guest bird in the Wadden Sea of ​​Denmark, Germany and the Netherlands, occasionally up to 200,000 individuals can be found. In the Baltic Sea area, on the other hand, there are only a very small number of knots.

description

The Knutt is a squat, blackbird-sized sandpiper with a short neck. It reaches a body length of 23 to 26 centimeters. The wingspan is 57 to 62 centimeters. The weight varies between 115 and 165 grams.

The beak is relatively short and straight. A pale, almost white ring runs around the base of the beak. The gray-green legs are short. When resting, the top of the bird is ash gray with light feather edges, the underside is whitish with faint gray stripes on the chest and flanks. In the summer breeding dress of both sexes, the upper side is black with reddish feather edges, the head and the underside are colored rusty red. In flight, the white wing bands and the gray-speckled rump and tail become visible. The plumage of the young birds resembles the resting plumage of the adult birds, but the upper side is brownish with black and white feather edges and a dark central line, the flanks are beige in color. The legs are colored olive yellow.

The downy cubs are white on the underside of their bodies. In some individuals, the throat is sand-colored. The head is cream-colored. The skull is irregularly spotted and streaked with brown. A dark line runs from the beak to the top of the head. The rein stripe is dark and narrow, underneath is a dark beard stripe. The neck is whitish and the back is marbled gray and black-brown and has numerous creamy white fine points. The iris is dark brown. The beak is yellowish with a blackish tip. The legs and toes are grayish yellow.

In the breeding dress Knutts resemble the Sickle Sandpiper , but Knutts are somewhat larger and more compact. They also have a shorter and, above all, straighter beak. Their feet are lighter than those of the sickle sandpiper.

habitat

The knutt breeds mainly in Greenland , Canada , Alaska and Siberia in the tundra . He is an extreme long-distance migrant and makes a stopover at the Wadden Sea on the North Sea coast in spring and autumn . Its wintering area is in south-west Africa.

Subspecies and their distribution

Distribution map and migration routes of the subspecies
Red-Knot (Calidris canutus) RWD2.jpg

There are six subspecies of knot (sorted by size here)

  • C. c. roselaari (largest)
  • C. c. rufa
  • C. c. canutus
  • C. c. islandica
  • C. c. rogersi
  • C. c. piersmai (smallest)

C. c. piersmai breeds in Northern Siberia and moves to northwest Australia, resting in the Yellow River Delta in China , where it hibernates on mud flats on the coast. C. c. rogersi breeds in the far northeast of Siberia and migrates, also along the Chinese coast, to southeast Australia and north New Zealand to winter. C. c. roselaari breeds in the far north of Alaska and moves across the Delaware Bay in the northeast of the USA to the wintering areas in Florida . It is currently not clear whether this subspecies migrates along the American Pacific coast, possibly to winter in Central America. The subspecies C. c. rufa breeds in northeast Canada, stops on the passage also in the bay of Delaware, and then moves to Argentina with another short rest in Brazil . C. c. islandica breeds in northern Greenland and flies, with a stop in Iceland and possibly also in Norway , to Great Britain and northwestern Europe, where this species winters on the vast mud flats in the Wadden Sea . The breeding area of C. c. canutus is located in Northern Siberia, however, to the west of the breeding area of C. c. piersmai . C. c. canutus migrates to West Africa, where it winters on mud flats along the coast. The Wadden Sea is an important resting area for this subspecies.

food

The diet consists mainly of mussels and mud flats. The knot swallows its prey completely and breaks the shells in the gizzard. In the breeding area, Knutts feed on soil arthropods .

Breeding biology

Knutts in her quiet dress
Knutt in youth dress
Calidris canutus
Knutts flying up

Knutts breed in the extensive tundra areas of Siberia, Greenland, Canada and Alaska. The birds breed sporadically, sometimes several kilometers apart. The female lays three to four eggs in a hollow on the floor padded with moss. Both parents breed on the nest, but the female leaves the nest shortly before the young hatch. The chicks flee nests and feed themselves from day one. As soon as the young fledglings, the male also begins to retreat to the winter areas. The young animals follow a few days or weeks later without the old animals.

Adaptations to an extreme way of life

The Knutt is one of the bird species that cover the longest distances between breeding, resting and wintering areas non-stop. These distances can be up to 5,000 kilometers. In order to accomplish this enormous feat, the knutt has developed some special skills and characteristics. Before such a long-haul flight, Knutts eat immense quantities on mud flats or mud flats. As a result, they gain up to twice their normal weight. Fat deposits are created all over the body, which give the bird energy during the non-stop flight. In order to create space in the body for this enormous fat reserve and to avoid unnecessary ballast, Knutts even shrink their internal organs. This is how Knutts can change the size of their gizzards. This change is triggered by the type of food the birds ingest. Ingesting hard foods, such as hard-shell clams, leads to an enlargement and strengthening of the muscles that crack these clamshells. Soft foods such as lugworms lead to a reduction in the size of the stomach and thus to a reduction in weight, which in turn enables the storage of more fat deposits and thus enables greater distances to be covered.

Duration

The total European population is estimated at around 15,000 to 30,000 breeding pairs. They breed almost exclusively on Greenland, a few pairs also breed on Svalbard.

supporting documents

literature

  • Hans-Günther Bauer, Einhard Bezzel and Wolfgang Fiedler (eds.): The compendium of birds in Central Europe: Everything about biology, endangerment and protection. Volume 1: Nonpasseriformes - non-sparrow birds. Aula-Verlag Wiebelsheim, Wiesbaden 2005, ISBN 3-89104-647-2 .
  • Peter Colston , Philip Burton: Limicolen - All European wader species, identifiers, flight images, biology, distribution. BlV Verlagsgesellschaft, Munich 1989, ISBN 3-405-13647-4
  • Simon Delany, Derek Scott, Tim Dodman, David Stroud (Eds.): An Atlas of Wader Populations in Africa and Western Eurasia. Wetlands International , Wageningen 2009, ISBN 978-90-5882-047-1 .
  • Collin Harrison and Peter Castell: Fledglings, Eggs and Nests of Birds in Europe, North Africa and the Middle East. Aula Verlag, Wiebelsheim 2004, ISBN 3-89104-685-5
  • Piersma, T., de Goeij, TP & Tulp, I. 1993 An evaluation of intertidal feeding habitats from a shorebird perspective: towards relevant comparisons between temperate and tropical mudflats. Netherlands Journal of Sea Research 31, 503-512.
  • Piersma, T., Dietz, MW, Dekinga, A., Nebel, S., van Gils, JA, Battley, PF & Spaans, B. 1999 Reversible size-changes in stomachs of shorebirds: when, to what extent, and why ? Acta Ornithologia 34, 175-181.
  • Richard Sale: A Complete Guide to Arctic Wildlife , published by Christopher Helm, London 2006, ISBN 0-7136-7039-8
  • Tomkovich, PS 1992 An analysis of the geographic variability in knots Calidris canutus based on museum skins. Wader Study Group Bulletin 64 Supplement, 17-23.
  • Tomkovich, PS 2001 A new subspecies of Red Knot Calidris canutus from the New Siberian Islands. Bulletin of the British Ornithologists Club 121, 257-263.
  • Tulp, I., Schekkerman, H., Piersma, T., Jukema, J., de Goeij, P. & van de Kam, J. 1998 Breeding waders at Cape Sterlegova, northern Taimyr, in 1994. Zeist: WIWO Report 61 .

Web links

Commons : Knutt ( Calidris canutus )  - Album with pictures, videos and audio files

Single receipts

  1. Sale, p. 183
  2. Harrison et al., P. 137
  3. Sale, p. 183
  4. Bauer et al., P. 525